diff --git a/src/material/expansion/_expansion-mixins.scss b/src/material/expansion/_expansion-mixins.scss
new file mode 100644
index 000000000000..cb515119e284
--- /dev/null
+++ b/src/material/expansion/_expansion-mixins.scss
@@ -0,0 +1,11 @@
+@mixin mat-private-expansion-focus {
+  .mat-expansion-panel {
+    & .mat-expansion-panel-header.cdk-keyboard-focused,
+    & .mat-expansion-panel-header.cdk-program-focused,
+    &:not(.mat-expanded) .mat-expansion-panel-header:hover {
+      &:not([aria-disabled='true']) {
+        @content;
+      }
+    }
+  }
+}
diff --git a/src/material/expansion/_expansion-theme.scss b/src/material/expansion/_expansion-theme.scss
index 914816ca07d1..5f52f956822c 100644
--- a/src/material/expansion/_expansion-theme.scss
+++ b/src/material/expansion/_expansion-theme.scss
@@ -4,6 +4,7 @@
 @import '../core/style/private';
 @import '../core/typography/typography-utils';
 @import './expansion-variables';
+@import './expansion-mixins';
 
 @mixin mat-expansion-panel-color($config-or-theme) {
   $config: mat-get-color-config($config-or-theme);
@@ -20,14 +21,8 @@
     border-top-color: mat-color($foreground, divider);
   }
 
-  .mat-expansion-panel {
-    & .mat-expansion-panel-header.cdk-keyboard-focused,
-    & .mat-expansion-panel-header.cdk-program-focused,
-    &:not(.mat-expanded) .mat-expansion-panel-header:hover {
-      &:not([aria-disabled='true']) {
-        background: mat-color($background, hover);
-      }
-    }
+  @include mat-private-expansion-focus {
+    background: mat-color($background, hover);
   }
 
   // Disable the hover on touch devices since it can appear like it is stuck. We can't use
diff --git a/src/material/expansion/expansion-panel-header.scss b/src/material/expansion/expansion-panel-header.scss
index 0cff73550702..fd3f4e2ec93c 100644
--- a/src/material/expansion/expansion-panel-header.scss
+++ b/src/material/expansion/expansion-panel-header.scss
@@ -1,4 +1,7 @@
+@import '../core/style/layout-common';
+@import '../../cdk/a11y/a11y';
 @import './expansion-variables';
+@import './expansion-mixins';
 
 .mat-expansion-panel-header {
   display: flex;
@@ -76,3 +79,19 @@
   transform: rotate(45deg);
   vertical-align: middle;
 }
+
+@include cdk-high-contrast(active, off) {
+  @include mat-private-expansion-focus {
+    &::before {
+      // These styles are identical to the ones generated for all
+      // `.mat-focus-indicator` when strong focus indication is enabled.
+      // We have to repeat them, because strong focus is opt-in.
+      @include mat-fill();
+      box-sizing: border-box;
+      pointer-events: none;
+      border: 3px solid;
+      border-radius: 4px;
+      content: '';
+    }
+  }
+}