diff --git a/common/changes/office-ui-fabric-react/wutonghao-UpdateColorPickerWhenAlphaIsHidden_2018-04-12-14-47.json b/common/changes/office-ui-fabric-react/wutonghao-UpdateColorPickerWhenAlphaIsHidden_2018-04-12-14-47.json
new file mode 100644
index 0000000000000..f91d3314e6eaf
--- /dev/null
+++ b/common/changes/office-ui-fabric-react/wutonghao-UpdateColorPickerWhenAlphaIsHidden_2018-04-12-14-47.json
@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "office-ui-fabric-react",
+      "comment": "ColorPicker: text fields now update when `alphaSliderHidden` is `true`.",
+      "type": "patch"
+    }
+  ],
+  "packageName": "office-ui-fabric-react",
+  "email": "wuthao@microsoft.com"
+}
diff --git a/packages/office-ui-fabric-react/src/components/ColorPicker/ColorPicker.tsx b/packages/office-ui-fabric-react/src/components/ColorPicker/ColorPicker.tsx
index 291607e1e8e5b..ef8869b4ddd80 100644
--- a/packages/office-ui-fabric-react/src/components/ColorPicker/ColorPicker.tsx
+++ b/packages/office-ui-fabric-react/src/components/ColorPicker/ColorPicker.tsx
@@ -166,7 +166,7 @@ export class ColorPicker extends BaseComponent<IColorPickerProps, IColorPickerSt
       r: Number(this.rText.value),
       g: Number(this.gText.value),
       b: Number(this.bText.value),
-      a: Number(this.aText.value)
+      a: Number((this.aText && this.aText.value) || 100)
     }));
   }