diff --git a/packages/material-ui/src/Step/Step.js b/packages/material-ui/src/Step/Step.js
index 1748a817df5ed0..370a464ecf8d34 100644
--- a/packages/material-ui/src/Step/Step.js
+++ b/packages/material-ui/src/Step/Step.js
@@ -25,6 +25,8 @@ export const styles = {
     flex: 1,
     position: 'relative',
   },
+  /* Styles applied to the root element if `completed={true}`. */
+  completed: {},
 };
 
 function Step(props) {
@@ -48,6 +50,7 @@ function Step(props) {
     classes[orientation],
     {
       [classes.alternativeLabel]: alternativeLabel,
+      [classes.completed]: completed,
     },
     classNameProp,
   );
diff --git a/pages/api/step.md b/pages/api/step.md
index 1efa061c7a31fb..a472f2c2606342 100644
--- a/pages/api/step.md
+++ b/pages/api/step.md
@@ -35,6 +35,7 @@ This property accepts the following keys:
 | <span class="prop-name">horizontal</span> | Styles applied to the root element if `orientation="horizontal"`.
 | <span class="prop-name">vertical</span> | Styles applied to the root element if `orientation="vertical"`.
 | <span class="prop-name">alternativeLabel</span> | Styles applied to the root element if `alternativeLabel={true}`.
+| <span class="prop-name">completed</span> | Styles applied to the root element if `completed={true}`.
 
 Have a look at [overriding with classes](/customization/overrides#overriding-with-classes) section
 and the [implementation of the component](https://github.com/mui-org/material-ui/tree/master/packages/material-ui/src/Step/Step.js)