diff --git a/change/@fluentui-react-cb9f45ee-a6ad-4ffc-afb6-62a53daac1fe.json b/change/@fluentui-react-cb9f45ee-a6ad-4ffc-afb6-62a53daac1fe.json
new file mode 100644
index 00000000000000..1e275446e2024d
--- /dev/null
+++ b/change/@fluentui-react-cb9f45ee-a6ad-4ffc-afb6-62a53daac1fe.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: ContextualMenu should not include headers and dividers in ARIA index calculations",
+  "packageName": "@fluentui/react",
+  "email": "sarah.higley@microsoft.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/react/src/components/ContextualMenu/ContextualMenu.base.tsx b/packages/react/src/components/ContextualMenu/ContextualMenu.base.tsx
index 5a96c925c444f8..7de3b215a108d0 100644
--- a/packages/react/src/components/ContextualMenu/ContextualMenu.base.tsx
+++ b/packages/react/src/components/ContextualMenu/ContextualMenu.base.tsx
@@ -71,6 +71,18 @@ const DEFAULT_PROPS: Partial<IContextualMenuProps> = {
   beakWidth: 16,
 };
 
+/* return number of menu items, excluding headers and dividers */
+function getItemCount(items: IContextualMenuItem[]): number {
+  let totalItemCount = 0;
+  for (const item of items) {
+    if (item.itemType !== ContextualMenuItemType.Divider && item.itemType !== ContextualMenuItemType.Header) {
+      const itemCount = item.customOnRenderListLength ? item.customOnRenderListLength : 1;
+      totalItemCount += itemCount;
+    }
+  }
+  return totalItemCount;
+}
+
 export function getSubmenuItems(
   item: IContextualMenuItem,
   options?: {
@@ -949,7 +961,7 @@ export const ContextualMenuBase: React.FunctionComponent<IContextualMenuProps> =
             key: `section-${sectionProps.title}-title`,
             itemType: ContextualMenuItemType.Header,
             text: sectionProps.title,
-            id: id,
+            id,
           };
           ariaLabelledby = id;
         } else {
@@ -975,23 +987,34 @@ export const ContextualMenuBase: React.FunctionComponent<IContextualMenuProps> =
       }
 
       if (sectionProps.items && sectionProps.items.length > 0) {
+        let correctedIndex = 0;
         return (
           <li role="presentation" key={sectionProps.key || sectionItem.key || `section-${index}`}>
             <div {...groupProps}>
               <ul className={menuClassNames.list} role="presentation">
                 {sectionProps.topDivider && renderSeparator(index, itemClassNames, true, true)}
                 {headerItem && renderListItem(headerItem, sectionItem.key || index, itemClassNames, sectionItem.title)}
-                {sectionProps.items.map((contextualMenuItem, itemsIndex) =>
-                  renderMenuItem(
+                {sectionProps.items.map((contextualMenuItem, itemsIndex) => {
+                  const menuItem = renderMenuItem(
                     contextualMenuItem,
                     itemsIndex,
-                    itemsIndex,
-                    sectionProps.items.length,
+                    correctedIndex,
+                    getItemCount(sectionProps.items),
                     hasCheckmarks,
                     hasIcons,
                     menuClassNames,
-                  ),
-                )}
+                  );
+                  if (
+                    contextualMenuItem.itemType !== ContextualMenuItemType.Divider &&
+                    contextualMenuItem.itemType !== ContextualMenuItemType.Header
+                  ) {
+                    const indexIncrease = contextualMenuItem.customOnRenderListLength
+                      ? contextualMenuItem.customOnRenderListLength
+                      : 1;
+                    correctedIndex += indexIncrease;
+                  }
+                  return menuItem;
+                })}
                 {sectionProps.bottomDivider && renderSeparator(index, itemClassNames, false, true)}
               </ul>
             </div>
@@ -1062,9 +1085,9 @@ export const ContextualMenuBase: React.FunctionComponent<IContextualMenuProps> =
         onItemMouseEnter: onItemMouseEnterBase,
         onItemMouseLeave: onMouseItemLeave,
         onItemMouseMove: onItemMouseMoveBase,
-        onItemMouseDown: onItemMouseDown,
-        executeItemClick: executeItemClick,
-        onItemKeyDown: onItemKeyDown,
+        onItemMouseDown,
+        executeItemClick,
+        onItemKeyDown,
         expandedMenuItemKey,
         openSubMenu,
         dismissSubMenu: onSubMenuDismiss,
@@ -1160,7 +1183,7 @@ export const ContextualMenuBase: React.FunctionComponent<IContextualMenuProps> =
       ? getMenuClassNames(theme!, className)
       : getClassNames(styles, {
           theme: theme!,
-          className: className,
+          className,
         });
 
     const hasIcons = itemsHaveIcons(items);
@@ -1217,13 +1240,7 @@ export const ContextualMenuBase: React.FunctionComponent<IContextualMenuProps> =
 
     // The menu should only return if items were provided, if no items were provided then it should not appear.
     if (items && items.length > 0) {
-      let totalItemCount = 0;
-      for (const item of items) {
-        if (item.itemType !== ContextualMenuItemType.Divider && item.itemType !== ContextualMenuItemType.Header) {
-          const itemCount = item.customOnRenderListLength ? item.customOnRenderListLength : 1;
-          totalItemCount += itemCount;
-        }
-      }
+      const totalItemCount = getItemCount(items);
 
       const calloutStyles = classNames.subComponentStyles
         ? (classNames.subComponentStyles.callout as IStyleFunctionOrObject<
diff --git a/packages/react/src/components/ContextualMenu/ContextualMenu.test.tsx b/packages/react/src/components/ContextualMenu/ContextualMenu.test.tsx
index c0b1a45a8b5772..02d07b21aecf46 100644
--- a/packages/react/src/components/ContextualMenu/ContextualMenu.test.tsx
+++ b/packages/react/src/components/ContextualMenu/ContextualMenu.test.tsx
@@ -470,7 +470,7 @@ describe('ContextualMenu', () => {
               className: 'SubMenuClass',
             },
           ],
-          onDismiss: onDismiss,
+          onDismiss,
         },
       },
     ];
@@ -742,6 +742,61 @@ describe('ContextualMenu', () => {
     expect(menuItems.length).toEqual(10);
   });
 
+  it('calculates index and total of menu items correctly', () => {
+    const items: IContextualMenuItem[] = [
+      { key: 'header', text: 'header', itemType: ContextualMenuItemType.Header },
+      { key: '1', text: 'One' },
+      { key: 'divider', itemType: ContextualMenuItemType.Divider },
+      { key: '2', text: 'Two' },
+    ];
+
+    ReactTestUtils.act(() => {
+      ReactTestUtils.renderIntoDocument<IContextualMenuProps>(<ContextualMenu items={items} />);
+    });
+
+    const menuItems = document.querySelectorAll('li button');
+    const total = menuItems[0].getAttribute('aria-setsize');
+    const index1 = menuItems[0].getAttribute('aria-posinset');
+    const index2 = menuItems[1].getAttribute('aria-posinset');
+
+    expect(total).toBe('2');
+    expect(index1).toBe('1');
+    expect(index2).toBe('2');
+  });
+
+  it('calculates index and total of menu items in a section correctly', () => {
+    const items: IContextualMenuItem[] = [
+      {
+        key: 'section1',
+        itemType: ContextualMenuItemType.Section,
+        sectionProps: {
+          topDivider: true,
+          bottomDivider: true,
+          title: 'Actions',
+          items: [
+            { key: 'header', text: 'header', itemType: ContextualMenuItemType.Header },
+            { key: '1', text: 'One' },
+            { key: 'divider', itemType: ContextualMenuItemType.Divider },
+            { key: '2', text: 'Two' },
+          ],
+        },
+      },
+    ];
+
+    ReactTestUtils.act(() => {
+      ReactTestUtils.renderIntoDocument<IContextualMenuProps>(<ContextualMenu items={items} />);
+    });
+
+    const menuItems = document.querySelectorAll('li button');
+    const total = menuItems[0].getAttribute('aria-setsize');
+    const index1 = menuItems[0].getAttribute('aria-posinset');
+    const index2 = menuItems[1].getAttribute('aria-posinset');
+
+    expect(total).toBe('2');
+    expect(index1).toBe('1');
+    expect(index2).toBe('2');
+  });
+
   describe('with links', () => {
     const testUrl = 'http://test.com';
     let items: IContextualMenuItem[];