diff --git a/common/changes/office-ui-fabric-react/kysedate-comboBox-getClassNamesProp_2018-01-20-02-14.json b/common/changes/office-ui-fabric-react/kysedate-comboBox-getClassNamesProp_2018-01-20-02-14.json
new file mode 100644
index 0000000000000..9c4b79fc3b8d3
--- /dev/null
+++ b/common/changes/office-ui-fabric-react/kysedate-comboBox-getClassNamesProp_2018-01-20-02-14.json
@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "office-ui-fabric-react",
+      "comment": "ComboBox: Add getClassNAmes prop to allow complete customization of the component",
+      "type": "patch"
+    }
+  ],
+  "packageName": "office-ui-fabric-react",
+  "email": "kysedate@microsoft.com"
+}
\ No newline at end of file
diff --git a/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.tsx b/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.tsx
index 22d0875891a1f..34f4311bd5f0d 100644
--- a/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.tsx
+++ b/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.tsx
@@ -281,16 +281,26 @@ export class ComboBox extends BaseComponent<IComboBoxProps, IComboBoxState> {
 
     let hasErrorMessage = (errorMessage && errorMessage.length > 0) ? true : false;
 
-    this._classNames = getClassNames(
-      getStyles(theme!, customStyles),
-      className!,
-      !!isOpen,
-      !!disabled,
-      !!required,
-      !!focused,
-      !!allowFreeform,
-      !!hasErrorMessage
-    );
+    this._classNames = this.props.getClassNames ?
+      this.props.getClassNames(
+        theme!,
+        !!isOpen,
+        !!disabled,
+        !!required,
+        !!focused,
+        !!allowFreeform,
+        !!hasErrorMessage,
+        className) :
+      getClassNames(
+        getStyles(theme!, customStyles),
+        className!,
+        !!isOpen,
+        !!disabled,
+        !!required,
+        !!focused,
+        !!allowFreeform,
+        !!hasErrorMessage
+      );
 
     return (
       <div {...divProps } ref='root' className={ this._classNames.container }>
diff --git a/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.types.ts b/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.types.ts
index 2abc4a44c830c..c2c5ce268d6e9 100644
--- a/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.types.ts
+++ b/packages/office-ui-fabric-react/src/components/ComboBox/ComboBox.types.ts
@@ -4,6 +4,7 @@ import { ISelectableDroppableTextProps } from '../../utilities/selectableOption/
 import { IStyle, ITheme } from '../../Styling';
 import { IButtonStyles } from '../../Button';
 import { IRenderFunction } from '../../Utilities';
+import { IComboBoxClassNames } from './ComboBox.classNames';
 
 export interface IComboBox {
   /**
@@ -101,6 +102,21 @@ export interface IComboBoxProps extends ISelectableDroppableTextProps<IComboBox>
    */
   styles?: Partial<IComboBoxStyles>;
 
+  /**
+   * Custom function for providing the classNames for the ComboBox. Can be used to provide
+   * all styles for the component instead of applying them on top of the default styles.
+   */
+  getClassNames?: (
+    theme: ITheme,
+    isOpen: boolean,
+    disabled: boolean,
+    required: boolean,
+    focused: boolean,
+    allowFreeForm: boolean,
+    hasErrorMessage: boolean,
+    className?: string
+  ) => IComboBoxClassNames;
+
   /**
    * Styles for the caret down button.
    */