diff --git a/common/changes/office-ui-fabric-react/focuszone_2019-04-02-01-01.json b/common/changes/office-ui-fabric-react/focuszone_2019-04-02-01-01.json
new file mode 100644
index 00000000000000..7ee9648cdb47a9
--- /dev/null
+++ b/common/changes/office-ui-fabric-react/focuszone_2019-04-02-01-01.json
@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "office-ui-fabric-react",
+      "comment": "FocusZone: fixing logic to track outer FZ components correctly.",
+      "type": "patch"
+    }
+  ],
+  "packageName": "office-ui-fabric-react",
+  "email": "dzearing@microsoft.com"
+}
\ No newline at end of file
diff --git a/packages/office-ui-fabric-react/etc/office-ui-fabric-react.api.md b/packages/office-ui-fabric-react/etc/office-ui-fabric-react.api.md
index 1aef39e7e783cf..bfb767bcd7da1a 100644
--- a/packages/office-ui-fabric-react/etc/office-ui-fabric-react.api.md
+++ b/packages/office-ui-fabric-react/etc/office-ui-fabric-react.api.md
@@ -1199,6 +1199,7 @@ export class FocusZone extends React.Component<IFocusZoneProps, {}> implements I
     static defaultProps: IFocusZoneProps;
     focus(forceIntoFirstElement?: boolean): boolean;
     focusElement(element: HTMLElement): boolean;
+    static getOuterZones(): number;
     // (undocumented)
     render(): JSX.Element;
     }
diff --git a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.test.tsx b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.test.tsx
index 38dbbca03d3b5d..b5a8fd247ad789 100644
--- a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.test.tsx
+++ b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.test.tsx
@@ -230,6 +230,28 @@ describe('FocusZone', () => {
     expect(document.activeElement).toBe(host.querySelector('#b'));
   });
 
+  it('only adds outerzones to be updated for tab changes', () => {
+    const activeZones = FocusZone.getOuterZones();
+
+    host = document.createElement('div');
+
+    // Render component without button A.
+    ReactDOM.render(
+      <FocusZone>
+        <FocusZone>
+          <button>ok</button>
+        </FocusZone>
+      </FocusZone>,
+      host
+    );
+
+    expect(FocusZone.getOuterZones()).toEqual(activeZones + 1);
+
+    ReactDOM.unmountComponentAtNode(host);
+
+    expect(FocusZone.getOuterZones()).toEqual(activeZones);
+  });
+
   it('can call onActiveItemChanged when the active item is changed', () => {
     let called = false;
     const component = ReactTestUtils.renderIntoDocument(
diff --git a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
index 06b46f229cd708..7e1577b7c7383f 100644
--- a/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
+++ b/packages/office-ui-fabric-react/src/components/FocusZone/FocusZone.tsx
@@ -79,6 +79,11 @@ export class FocusZone extends React.Component<IFocusZoneProps, {}> implements I
   /** Used to allow us to move to next focusable element even when we're focusing on a input element when pressing tab */
   private _processingTabKey: boolean;
 
+  /** Used for testing purposes only. */
+  public static getOuterZones(): number {
+    return _outerZones.size;
+  }
+
   constructor(props: IFocusZoneProps) {
     super(props);
 
@@ -108,10 +113,6 @@ export class FocusZone extends React.Component<IFocusZoneProps, {}> implements I
 
     _allInstances[this._id] = this;
 
-    if (!this._isInnerZone) {
-      _outerZones.add(this);
-    }
-
     if (root) {
       const windowElement = root.ownerDocument!.defaultView;
 
@@ -125,6 +126,10 @@ export class FocusZone extends React.Component<IFocusZoneProps, {}> implements I
         parentElement = getParent(parentElement, ALLOW_VIRTUAL_ELEMENTS);
       }
 
+      if (!this._isInnerZone) {
+        _outerZones.add(this);
+      }
+
       if (windowElement && _outerZones.size === 1) {
         this._disposables.push(on(windowElement, 'keydown', this._onKeyDownCapture, true));
       }