diff --git a/packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts b/packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts
index ebd84c87f1366..6f751998af367 100644
--- a/packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts
+++ b/packages/@aws-cdk/aws-codepipeline/lib/pipeline.ts
@@ -336,6 +336,18 @@ export class Pipeline extends PipelineBase {
     return this._stages.slice();
   }
 
+  /**
+   * Access one of the pipeline's stages by stage name
+   */
+  public stage(stageName: string): IStage {
+    for (const stage of this._stages) {
+      if (stage.stageName === stageName) {
+        return stage;
+      }
+    }
+    throw new Error(`Pipeline does not contain a stage named '${stageName}'. Available stages: ${this._stages.map(s => s.stageName).join(', ')}`);
+  }
+
   /**
    * Returns all of the {@link CrossRegionSupportStack}s that were generated automatically
    * when dealing with Actions that reside in a different region than the Pipeline itself.
diff --git a/packages/@aws-cdk/aws-codepipeline/test/pipeline.test.ts b/packages/@aws-cdk/aws-codepipeline/test/pipeline.test.ts
index ab360b80e3038..880c45b1f8a05 100644
--- a/packages/@aws-cdk/aws-codepipeline/test/pipeline.test.ts
+++ b/packages/@aws-cdk/aws-codepipeline/test/pipeline.test.ts
@@ -1,4 +1,5 @@
-import { expect, haveResourceLike, ResourcePart } from '@aws-cdk/assert';
+import { expect as ourExpect, ResourcePart, arrayWith, objectLike, haveResourceLike } from '@aws-cdk/assert';
+import '@aws-cdk/assert/jest';
 import * as iam from '@aws-cdk/aws-iam';
 import * as kms from '@aws-cdk/aws-kms';
 import * as s3 from '@aws-cdk/aws-s3';
@@ -22,7 +23,7 @@ nodeunitShim({
         role,
       });
 
-      expect(stack, true).to(haveResourceLike('AWS::CodePipeline::Pipeline', {
+      ourExpect(stack, true).to(haveResourceLike('AWS::CodePipeline::Pipeline', {
         'RoleArn': {
           'Fn::GetAtt': [
             'Role1ABCC5F0',
@@ -109,7 +110,7 @@ nodeunitShim({
           ],
         });
 
-        expect(pipelineStack).to(haveResourceLike('AWS::CodePipeline::Pipeline', {
+        expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
           'ArtifactStores': [
             {
               'Region': replicationRegion,
@@ -136,9 +137,9 @@ nodeunitShim({
               'Region': pipelineRegion,
             },
           ],
-        }));
+        });
 
-        expect(replicationStack).to(haveResourceLike('AWS::KMS::Key', {
+        expect(replicationStack).toHaveResourceLike('AWS::KMS::Key', {
           'KeyPolicy': {
             'Statement': [
               {
@@ -170,7 +171,7 @@ nodeunitShim({
               },
             ],
           },
-        }));
+        });
 
         test.done();
       },
@@ -204,7 +205,7 @@ nodeunitShim({
           ],
         });
 
-        expect(pipelineStack).to(haveResourceLike('AWS::CodePipeline::Pipeline', {
+        expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
           'ArtifactStores': [
             {
               'Region': replicationRegion,
@@ -231,12 +232,12 @@ nodeunitShim({
               'Region': pipelineRegion,
             },
           ],
-        }));
+        });
 
-        expect(pipeline.crossRegionSupport[replicationRegion].stack).to(haveResourceLike('AWS::KMS::Alias', {
+        expect(pipeline.crossRegionSupport[replicationRegion].stack).toHaveResourceLike('AWS::KMS::Alias', {
           'DeletionPolicy': 'Delete',
           'UpdateReplacePolicy': 'Delete',
-        }, ResourcePart.CompleteDefinition));
+        }, ResourcePart.CompleteDefinition);
 
         test.done();
       },
@@ -276,7 +277,7 @@ nodeunitShim({
           ],
         });
 
-        expect(pipelineStack).to(haveResourceLike('AWS::CodePipeline::Pipeline', {
+        expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
           'ArtifactStores': [
             {
               'Region': replicationRegion,
@@ -293,7 +294,7 @@ nodeunitShim({
               'Region': pipelineRegion,
             },
           ],
-        }));
+        });
 
         test.done();
       },
@@ -392,3 +393,42 @@ nodeunitShim({
     },
   },
 });
+
+describe('test with shared setup', () => {
+  let stack: cdk.Stack;
+  let sourceArtifact: codepipeline.Artifact;
+  beforeEach(() => {
+    stack = new cdk.Stack();
+    sourceArtifact = new codepipeline.Artifact();
+  });
+
+  test('can add actions to stages after creation', () => {
+    // GIVEN
+    const pipeline = new codepipeline.Pipeline(stack, 'Pipeline', {
+      stages: [
+        {
+          stageName: 'Source',
+          actions: [new FakeSourceAction({ actionName: 'Fetch', output: sourceArtifact })],
+        },
+        {
+          stageName: 'Build',
+          actions: [new FakeBuildAction({ actionName: 'Gcc', input: sourceArtifact })],
+        },
+      ],
+    });
+
+    // WHEN
+    pipeline.stage('Build').addAction(new FakeBuildAction({ actionName: 'debug.com', input: sourceArtifact }));
+
+    // THEN
+    expect(stack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
+      Stages: arrayWith({
+        Name: 'Build',
+        Actions: [
+          objectLike({ Name: 'Gcc' }),
+          objectLike({ Name: 'debug.com' }),
+        ],
+      }),
+    });
+  });
+});
diff --git a/packages/@aws-cdk/pipelines/README.md b/packages/@aws-cdk/pipelines/README.md
index 9905468d891f1..8f19d40253bfb 100644
--- a/packages/@aws-cdk/pipelines/README.md
+++ b/packages/@aws-cdk/pipelines/README.md
@@ -152,6 +152,29 @@ new MyPipelineStack(this, 'PipelineStack', {
 });
 ```
 
+If you prefer more control over the underlying CodePipeline object, you can
+create one yourself, including custom Source and Build stages:
+
+```ts
+const codePipeline = new cp.Pipeline(pipelineStack, 'CodePipeline', {
+  stages: [
+    {
+      stageName: 'CustomSource',
+      actions: [...],
+    },
+    {
+      stageName: 'CustomBuild',
+      actions: [...],
+    },
+  ],
+});
+
+const cdkPipeline = new CdkPipeline(this, 'CdkPipeline', {
+  codePipeline,
+  cloudAssemblyArtifact,
+});
+```
+
 ## Initial pipeline deployment
 
 You provision this pipeline by making sure the target environment has been
diff --git a/packages/@aws-cdk/pipelines/lib/pipeline.ts b/packages/@aws-cdk/pipelines/lib/pipeline.ts
index 7f9de4aca71c4..6355d836c15c8 100644
--- a/packages/@aws-cdk/pipelines/lib/pipeline.ts
+++ b/packages/@aws-cdk/pipelines/lib/pipeline.ts
@@ -12,22 +12,44 @@ import { AddStageOptions, AssetPublishingCommand, CdkStage, StackOutput } from '
 export interface CdkPipelineProps {
   /**
    * The CodePipeline action used to retrieve the CDK app's source
+   *
+   * @default - Required unless `codePipeline` is given
    */
-  readonly sourceAction: codepipeline.IAction;
+  readonly sourceAction?: codepipeline.IAction;
 
   /**
    * The CodePipeline action build and synthesis step of the CDK app
+   *
+   * @default - Required unless `codePipeline` or `sourceAction` is given
    */
-  readonly synthAction: codepipeline.IAction;
+  readonly synthAction?: codepipeline.IAction;
 
   /**
    * The artifact you have defined to be the artifact to hold the cloudAssemblyArtifact for the synth action
    */
   readonly cloudAssemblyArtifact: codepipeline.Artifact;
 
+  /**
+   * Existing CodePipeline to add deployment stages to
+   *
+   * Use this if you want more control over the CodePipeline that gets created.
+   * You can choose to not pass this value, in which case a new CodePipeline is
+   * created with default settings.
+   *
+   * If you pass an existing CodePipeline, it should should have been created
+   * with `restartExecutionOnUpdate: true`.
+   *
+   * [disable-awslint:ref-via-interface]
+   *
+   * @default - A new CodePipeline is automatically generated
+   */
+  readonly codePipeline?: codepipeline.Pipeline;
+
   /**
    * Name of the pipeline
    *
+   * Can only be set if `codePipeline` is not set.
+   *
    * @default - A name is automatically generated
    */
   readonly pipelineName?: string;
@@ -72,28 +94,58 @@ export class CdkPipeline extends Construct {
     this._cloudAssemblyArtifact = props.cloudAssemblyArtifact;
     const pipelineStack = Stack.of(this);
 
-    this._pipeline = new codepipeline.Pipeline(this, 'Pipeline', {
-      ...props,
-      restartExecutionOnUpdate: true,
-      stages: [
-        {
-          stageName: 'Source',
-          actions: [props.sourceAction],
-        },
-        {
-          stageName: 'Build',
-          actions: [props.synthAction],
-        },
-        {
-          stageName: 'UpdatePipeline',
-          actions: [new UpdatePipelineAction(this, 'UpdatePipeline', {
-            cloudAssemblyInput: this._cloudAssemblyArtifact,
-            pipelineStackName: pipelineStack.stackName,
-            cdkCliVersion: props.cdkCliVersion,
-            projectName: maybeSuffix(props.pipelineName, '-selfupdate'),
-          })],
-        },
-      ],
+    if (props.codePipeline) {
+      if (props.pipelineName) {
+        throw new Error('Cannot set \'pipelineName\' if an existing CodePipeline is given using \'codePipeline\'');
+      }
+
+      this._pipeline = props.codePipeline;
+    } else {
+      this._pipeline = new codepipeline.Pipeline(this, 'Pipeline', {
+        pipelineName: props.pipelineName,
+        restartExecutionOnUpdate: true,
+      });
+    }
+
+    if (props.sourceAction && !props.synthAction) {
+      // Because of ordering limitations, you can: bring your own Source, bring your own
+      // Both, or bring your own Nothing. You cannot bring your own Build (which because of the
+      // current CodePipeline API must go BEFORE what we're adding) and then having us add a
+      // Source after it. That doesn't make any sense.
+      throw new Error('When passing a \'sourceAction\' you must also pass a \'synthAction\' (or a \'codePipeline\' that already has both)');
+    }
+    if (!props.sourceAction && (!props.codePipeline || props.codePipeline.stages.length < 1)) {
+      throw new Error('You must pass a \'sourceAction\' (or a \'codePipeline\' that already has a Source stage)');
+    }
+    if (!props.synthAction && (!props.codePipeline || props.codePipeline.stages.length < 2)) {
+      // This looks like a weirdly specific requirement, but actually the underlying CodePipeline
+      // requires that a Pipeline has at least 2 stages. We're just hitching onto upstream
+      // requirements to do this check.
+      throw new Error('You must pass a \'synthAction\' (or a \'codePipeline\' that already has a Build stage)');
+    }
+
+    if (props.sourceAction) {
+      this._pipeline.addStage({
+        stageName: 'Source',
+        actions: [props.sourceAction],
+      });
+    }
+
+    if (props.synthAction) {
+      this._pipeline.addStage({
+        stageName: 'Build',
+        actions: [props.synthAction],
+      });
+    }
+
+    this._pipeline.addStage({
+      stageName: 'UpdatePipeline',
+      actions: [new UpdatePipelineAction(this, 'UpdatePipeline', {
+        cloudAssemblyInput: this._cloudAssemblyArtifact,
+        pipelineStackName: pipelineStack.stackName,
+        cdkCliVersion: props.cdkCliVersion,
+        projectName: maybeSuffix(props.pipelineName, '-selfupdate'),
+      })],
     });
 
     this._assets = new AssetPublishing(this, 'Assets', {
@@ -112,10 +164,19 @@ export class CdkPipeline extends Construct {
    * You can use this to add more Stages to the pipeline, or Actions
    * to Stages.
    */
-  public get pipeline(): codepipeline.Pipeline {
+  public get codePipeline(): codepipeline.Pipeline {
     return this._pipeline;
   }
 
+  /**
+   * Access one of the pipeline's stages by stage name
+   *
+   * You can use this to add more Actions to a stage.
+   */
+  public stage(stageName: string): codepipeline.IStage {
+    return this._pipeline.stage(stageName);
+  }
+
   /**
    * Add pipeline stage that will deploy the given application stage
    *
diff --git a/packages/@aws-cdk/pipelines/test/existing-pipeline.test.ts b/packages/@aws-cdk/pipelines/test/existing-pipeline.test.ts
new file mode 100644
index 0000000000000..e9e6ed833e680
--- /dev/null
+++ b/packages/@aws-cdk/pipelines/test/existing-pipeline.test.ts
@@ -0,0 +1,127 @@
+import { objectLike } from '@aws-cdk/assert';
+import '@aws-cdk/assert/jest';
+import * as cp from '@aws-cdk/aws-codepipeline';
+import { Stack } from '@aws-cdk/core';
+import * as cdkp from '../lib';
+import { PIPELINE_ENV, TestApp, TestGitHubAction } from './testutil';
+
+let app: TestApp;
+let pipelineStack: Stack;
+let sourceArtifact: cp.Artifact;
+let cloudAssemblyArtifact: cp.Artifact;
+let codePipeline: cp.Pipeline;
+
+beforeEach(() => {
+  app = new TestApp();
+  pipelineStack = new Stack(app, 'PipelineStack', { env: PIPELINE_ENV });
+  sourceArtifact = new cp.Artifact();
+  cloudAssemblyArtifact = new cp.Artifact();
+});
+
+afterEach(() => {
+  app.cleanup();
+});
+
+describe('with empty existing CodePipeline', () => {
+  beforeEach(() => {
+    codePipeline = new cp.Pipeline(pipelineStack, 'CodePipeline');
+  });
+
+  test('both actions are required', () => {
+    // WHEN
+    expect(() => {
+      new cdkp.CdkPipeline(pipelineStack, 'Cdk', { cloudAssemblyArtifact, codePipeline });
+    }).toThrow(/You must pass a 'sourceAction'/);
+  });
+
+  test('can give both actions', () => {
+    // WHEN
+    new cdkp.CdkPipeline(pipelineStack, 'Cdk', {
+      cloudAssemblyArtifact,
+      codePipeline,
+      sourceAction: new TestGitHubAction(sourceArtifact),
+      synthAction: cdkp.SimpleSynthAction.standardNpmSynth({ sourceArtifact, cloudAssemblyArtifact }),
+    });
+
+    // THEN
+    expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
+      Stages: [
+        objectLike({ Name: 'Source' }),
+        objectLike({ Name: 'Build' }),
+        objectLike({ Name: 'UpdatePipeline' }),
+      ],
+    });
+  });
+});
+
+describe('with custom Source stage in existing Pipeline', () => {
+  beforeEach(() => {
+    codePipeline = new cp.Pipeline(pipelineStack, 'CodePipeline', {
+      stages: [
+        {
+          stageName: 'CustomSource',
+          actions: [new TestGitHubAction(sourceArtifact)],
+        },
+      ],
+    });
+  });
+
+  test('synth action is required', () => {
+    // WHEN
+    expect(() => {
+      new cdkp.CdkPipeline(pipelineStack, 'Cdk', { cloudAssemblyArtifact, codePipeline });
+    }).toThrow(/You must pass a 'synthAction'/);
+  });
+
+  test('Work with synthAction', () => {
+    // WHEN
+    new cdkp.CdkPipeline(pipelineStack, 'Cdk', {
+      codePipeline,
+      cloudAssemblyArtifact,
+      synthAction: cdkp.SimpleSynthAction.standardNpmSynth({ sourceArtifact, cloudAssemblyArtifact }),
+    });
+
+    // THEN
+    expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
+      Stages: [
+        objectLike({ Name: 'CustomSource' }),
+        objectLike({ Name: 'Build' }),
+        objectLike({ Name: 'UpdatePipeline' }),
+      ],
+    });
+  });
+});
+
+describe('with Source and Build stages in existing Pipeline', () => {
+  beforeEach(() => {
+    codePipeline = new cp.Pipeline(pipelineStack, 'CodePipeline', {
+      stages: [
+        {
+          stageName: 'CustomSource',
+          actions: [new TestGitHubAction(sourceArtifact)],
+        },
+        {
+          stageName: 'CustomBuild',
+          actions: [cdkp.SimpleSynthAction.standardNpmSynth({ sourceArtifact, cloudAssemblyArtifact })],
+        },
+      ],
+    });
+  });
+
+  test('can supply no actions', () => {
+    // WHEN
+    new cdkp.CdkPipeline(pipelineStack, 'Cdk', {
+      codePipeline,
+      cloudAssemblyArtifact,
+    });
+
+    // THEN
+    expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
+      Stages: [
+        objectLike({ Name: 'CustomSource' }),
+        objectLike({ Name: 'CustomBuild' }),
+        objectLike({ Name: 'UpdatePipeline' }),
+      ],
+    });
+  });
+});
\ No newline at end of file
diff --git a/packages/@aws-cdk/pipelines/test/pipeline.test.ts b/packages/@aws-cdk/pipelines/test/pipeline.test.ts
index 3f216464c55ed..7719620706cc6 100644
--- a/packages/@aws-cdk/pipelines/test/pipeline.test.ts
+++ b/packages/@aws-cdk/pipelines/test/pipeline.test.ts
@@ -1,6 +1,8 @@
 import { anything, arrayWith, deepObjectLike, encodedJson, objectLike, stringLike } from '@aws-cdk/assert';
 import '@aws-cdk/assert/jest';
-import { Construct, Stack, Stage, StageProps } from '@aws-cdk/core';
+import * as cp from '@aws-cdk/aws-codepipeline';
+import * as cpa from '@aws-cdk/aws-codepipeline-actions';
+import { Construct, Stack, Stage, StageProps, SecretValue } from '@aws-cdk/core';
 import * as cdkp from '../lib';
 import { BucketStack, PIPELINE_ENV, stackTemplate, TestApp, TestGitHubNpmPipeline } from './testutil';
 
@@ -373,6 +375,28 @@ test('can control fix/CLI version used in pipeline selfupdate', () => {
   });
 });
 
+test('add another action to an existing stage', () => {
+  // WHEN
+  pipeline.stage('Source').addAction(new cpa.GitHubSourceAction({
+    actionName: 'GitHub2',
+    oauthToken: SecretValue.plainText('oops'),
+    output: new cp.Artifact(),
+    owner: 'OWNER',
+    repo: 'REPO',
+  }));
+
+  // THEN
+  expect(pipelineStack).toHaveResourceLike('AWS::CodePipeline::Pipeline', {
+    Stages: arrayWith({
+      Name: 'Source',
+      Actions: [
+        objectLike({ Name: 'GitHub' }),
+        objectLike({ Name: 'GitHub2' }),
+      ],
+    }),
+  });
+});
+
 class OneStackApp extends Stage {
   constructor(scope: Construct, id: string, props?: StageProps) {
     super(scope, id, props);
diff --git a/packages/@aws-cdk/pipelines/test/testutil.ts b/packages/@aws-cdk/pipelines/test/testutil.ts
index ca5cb3db0e672..beb6e0180fa87 100644
--- a/packages/@aws-cdk/pipelines/test/testutil.ts
+++ b/packages/@aws-cdk/pipelines/test/testutil.ts
@@ -40,14 +40,7 @@ export class TestGitHubNpmPipeline extends cdkp.CdkPipeline {
     const cloudAssemblyArtifact = props?.cloudAssemblyArtifact ?? new codepipeline.Artifact();
 
     super(scope, id, {
-      sourceAction: new codepipeline_actions.GitHubSourceAction({
-        actionName: 'GitHub',
-        output: sourceArtifact,
-        oauthToken: SecretValue.plainText('$3kr1t'),
-        owner: 'test',
-        repo: 'test',
-        trigger: codepipeline_actions.GitHubTrigger.POLL,
-      }),
+      sourceAction: new TestGitHubAction(sourceArtifact),
       synthAction: cdkp.SimpleSynthAction.standardNpmSynth({
         sourceArtifact,
         cloudAssemblyArtifact,
@@ -61,6 +54,20 @@ export class TestGitHubNpmPipeline extends cdkp.CdkPipeline {
   }
 }
 
+
+export class TestGitHubAction extends codepipeline_actions.GitHubSourceAction {
+  constructor(sourceArtifact: codepipeline.Artifact) {
+    super({
+      actionName: 'GitHub',
+      output: sourceArtifact,
+      oauthToken: SecretValue.plainText('$3kr1t'),
+      owner: 'test',
+      repo: 'test',
+      trigger: codepipeline_actions.GitHubTrigger.POLL,
+    });
+  }
+}
+
 /**
  * A test stack
  *