diff --git a/src/material-experimental/mdc-menu/menu.spec.ts b/src/material-experimental/mdc-menu/menu.spec.ts
index ba04404b949b..f371f990bed1 100644
--- a/src/material-experimental/mdc-menu/menu.spec.ts
+++ b/src/material-experimental/mdc-menu/menu.spec.ts
@@ -32,7 +32,7 @@ import {
   MockNgZone,
 } from '@angular/cdk/testing/private';
 import {Subject} from 'rxjs';
-import {ScrollDispatcher} from '@angular/cdk/scrolling';
+import {ScrollDispatcher, ViewportRuler} from '@angular/cdk/scrolling';
 import {FocusMonitor} from '@angular/cdk/a11y';
 import {
   MAT_MENU_SCROLL_STRATEGY,
@@ -49,6 +49,7 @@ describe('MDC-based MatMenu', () => {
   let overlayContainer: OverlayContainer;
   let overlayContainerElement: HTMLElement;
   let focusMonitor: FocusMonitor;
+  let viewportRuler: ViewportRuler;
 
   function createComponent<T>(component: Type<T>,
                               providers: Provider[] = [],
@@ -59,11 +60,13 @@ describe('MDC-based MatMenu', () => {
       providers
     }).compileComponents();
 
-    inject([OverlayContainer, FocusMonitor], (oc: OverlayContainer, fm: FocusMonitor) => {
-      overlayContainer = oc;
-      overlayContainerElement = oc.getContainerElement();
-      focusMonitor = fm;
-    })();
+    inject([OverlayContainer, FocusMonitor, ViewportRuler],
+      (oc: OverlayContainer, fm: FocusMonitor, vr: ViewportRuler) => {
+        overlayContainer = oc;
+        overlayContainerElement = oc.getContainerElement();
+        focusMonitor = fm;
+        viewportRuler = vr;
+      })();
 
     return TestBed.createComponent<T>(component);
   }
@@ -1014,6 +1017,28 @@ describe('MDC-based MatMenu', () => {
         .toBe(false);
   });
 
+  it('should keep the panel in the viewport when more items are added while open', () => {
+    const fixture = createComponent(SimpleMenu, [], [FakeIcon]);
+    fixture.detectChanges();
+
+    const triggerEl = fixture.componentInstance.triggerEl.nativeElement;
+    triggerEl.style.position = 'absolute';
+    triggerEl.style.left = '200px';
+    triggerEl.style.bottom = '300px';
+    triggerEl.click();
+    fixture.detectChanges();
+
+    const panel = overlayContainerElement.querySelector('.mat-mdc-menu-panel')!;
+    const viewportHeight = viewportRuler.getViewportSize().height;
+    let panelRect = panel.getBoundingClientRect();
+    expect(Math.floor(panelRect.bottom)).toBeLessThan(viewportHeight);
+
+    fixture.componentInstance.extraItems = new Array(50).fill('Hello there');
+    fixture.detectChanges();
+    panelRect = panel.getBoundingClientRect();
+    expect(Math.floor(panelRect.bottom)).toBe(viewportHeight);
+  });
+
   describe('lazy rendering', () => {
     it('should be able to render the menu content lazily', fakeAsync(() => {
       const fixture = createComponent(SimpleLazyMenu);
diff --git a/src/material/menu/menu-trigger.ts b/src/material/menu/menu-trigger.ts
index 06de01f4fb1d..2bb4877d33f0 100644
--- a/src/material/menu/menu-trigger.ts
+++ b/src/material/menu/menu-trigger.ts
@@ -248,8 +248,9 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
 
     const overlayRef = this._createOverlay();
     const overlayConfig = overlayRef.getConfig();
+    const positionStrategy = overlayConfig.positionStrategy as FlexibleConnectedPositionStrategy;
 
-    this._setPosition(overlayConfig.positionStrategy as FlexibleConnectedPositionStrategy);
+    this._setPosition(positionStrategy);
     overlayConfig.hasBackdrop = this.menu.hasBackdrop == null ? !this.triggersSubmenu() :
         this.menu.hasBackdrop;
     overlayRef.attach(this._getPortal());
@@ -263,6 +264,12 @@ export class MatMenuTrigger implements AfterContentInit, OnDestroy {
 
     if (this.menu instanceof _MatMenuBase) {
       this.menu._startAnimation();
+      this.menu._directDescendantItems.changes.pipe(takeUntil(this.menu.close)).subscribe(() => {
+        // Re-adjust the position without locking when the amount of items
+        // changes so that the overlay is allowed to pick a new optimal position.
+        positionStrategy.withLockedPosition(false).reapplyLastPosition();
+        positionStrategy.withLockedPosition(true);
+      });
     }
   }
 
diff --git a/src/material/menu/menu.spec.ts b/src/material/menu/menu.spec.ts
index 388005dc6a38..70f07984db4c 100644
--- a/src/material/menu/menu.spec.ts
+++ b/src/material/menu/menu.spec.ts
@@ -2,7 +2,7 @@ import {FocusMonitor} from '@angular/cdk/a11y';
 import {Direction, Directionality} from '@angular/cdk/bidi';
 import {DOWN_ARROW, END, ESCAPE, HOME, LEFT_ARROW, RIGHT_ARROW, TAB} from '@angular/cdk/keycodes';
 import {Overlay, OverlayContainer} from '@angular/cdk/overlay';
-import {ScrollDispatcher} from '@angular/cdk/scrolling';
+import {ScrollDispatcher, ViewportRuler} from '@angular/cdk/scrolling';
 import {
   createKeyboardEvent,
   createMouseEvent,
@@ -50,6 +50,7 @@ describe('MatMenu', () => {
   let overlayContainer: OverlayContainer;
   let overlayContainerElement: HTMLElement;
   let focusMonitor: FocusMonitor;
+  let viewportRuler: ViewportRuler;
 
   function createComponent<T>(component: Type<T>,
                               providers: Provider[] = [],
@@ -60,11 +61,13 @@ describe('MatMenu', () => {
       providers
     }).compileComponents();
 
-    inject([OverlayContainer, FocusMonitor], (oc: OverlayContainer, fm: FocusMonitor) => {
-      overlayContainer = oc;
-      overlayContainerElement = oc.getContainerElement();
-      focusMonitor = fm;
-    })();
+    inject([OverlayContainer, FocusMonitor, ViewportRuler],
+      (oc: OverlayContainer, fm: FocusMonitor, vr: ViewportRuler) => {
+        overlayContainer = oc;
+        overlayContainerElement = oc.getContainerElement();
+        focusMonitor = fm;
+        viewportRuler = vr;
+      })();
 
     return TestBed.createComponent<T>(component);
   }
@@ -957,6 +960,28 @@ describe('MatMenu', () => {
         .toBe(false);
   });
 
+  it('should keep the panel in the viewport when more items are added while open', () => {
+    const fixture = createComponent(SimpleMenu, [], [FakeIcon]);
+    fixture.detectChanges();
+
+    const triggerEl = fixture.componentInstance.triggerEl.nativeElement;
+    triggerEl.style.position = 'absolute';
+    triggerEl.style.left = '200px';
+    triggerEl.style.bottom = '300px';
+    triggerEl.click();
+    fixture.detectChanges();
+
+    const panel = overlayContainerElement.querySelector('.mat-menu-panel')!;
+    const viewportHeight = viewportRuler.getViewportSize().height;
+    let panelRect = panel.getBoundingClientRect();
+    expect(Math.floor(panelRect.bottom)).toBeLessThan(viewportHeight);
+
+    fixture.componentInstance.extraItems = new Array(50).fill('Hello there');
+    fixture.detectChanges();
+    panelRect = panel.getBoundingClientRect();
+    expect(Math.floor(panelRect.bottom)).toBe(viewportHeight);
+  });
+
   describe('lazy rendering', () => {
     it('should be able to render the menu content lazily', fakeAsync(() => {
       const fixture = createComponent(SimpleLazyMenu);
diff --git a/src/material/menu/menu.ts b/src/material/menu/menu.ts
index b33a4409df47..b160bd0dad36 100644
--- a/src/material/menu/menu.ts
+++ b/src/material/menu/menu.ts
@@ -106,7 +106,7 @@ export class _MatMenuBase implements AfterContentInit, MatMenuPanel<MatMenuItem>
   @ContentChildren(MatMenuItem, {descendants: true}) _allItems: QueryList<MatMenuItem>;
 
   /** Only the direct descendant menu items. */
-  private _directDescendantItems = new QueryList<MatMenuItem>();
+  _directDescendantItems = new QueryList<MatMenuItem>();
 
   /** Subscription to tab events on the menu panel */
   private _tabSubscription = Subscription.EMPTY;
diff --git a/tools/public_api_guard/material/menu.d.ts b/tools/public_api_guard/material/menu.d.ts
index 009ff481e689..8383f91041bc 100644
--- a/tools/public_api_guard/material/menu.d.ts
+++ b/tools/public_api_guard/material/menu.d.ts
@@ -4,6 +4,7 @@ export declare class _MatMenuBase implements AfterContentInit, MatMenuPanel<MatM
     _classList: {
         [key: string]: boolean;
     };
+    _directDescendantItems: QueryList<MatMenuItem>;
     _isAnimating: boolean;
     _panelAnimationState: 'void' | 'enter';
     ariaDescribedby: string;