diff --git a/packages/babel-helper-annotate-as-pure/.npmignore b/packages/babel-helper-annotate-as-pure/.npmignore
new file mode 100644
index 0000000000..f980694583
--- /dev/null
+++ b/packages/babel-helper-annotate-as-pure/.npmignore
@@ -0,0 +1,3 @@
+src
+test
+*.log
diff --git a/packages/babel-helper-annotate-as-pure/README.md b/packages/babel-helper-annotate-as-pure/README.md
new file mode 100644
index 0000000000..2b52b189bb
--- /dev/null
+++ b/packages/babel-helper-annotate-as-pure/README.md
@@ -0,0 +1,36 @@
+# babel-helper-annotate-as-pure
+
+## API
+
+```js
+declare export default annotateAsPure(nodeOrPath: Node | NodePath);
+```
+
+## Usage
+
+```js
+import traverse from "babel-traverse";
+import annotateAsPure from "babel-helper-annotate-as-pure";
+
+// ...
+
+traverse(file, {
+  CallExpression(path) {
+    annotateAsPure(path);
+  },
+});
+```
+
+## Caveat with UglifyJS pre v3.1.0
+
+`babel-helper-annotate-as-pure` concatenates existing leading comments to the `#__PURE__` annotation, but versions of UglifyJS before v3.1.0 checks only the last leading comment for the annotation.
+
+So for the example input when annotating all CallExpressions:
+```js
+const four = /* foo */ add(2, 2);
+```
+it produces:
+```js
+const four = /* #__PURE__ */ /* foo */ add(2, 2);
+```
+and such generated annotation will be ignored in those previous versions of the UglifyJS.
diff --git a/packages/babel-helper-annotate-as-pure/package.json b/packages/babel-helper-annotate-as-pure/package.json
new file mode 100644
index 0000000000..744f32e825
--- /dev/null
+++ b/packages/babel-helper-annotate-as-pure/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "babel-helper-annotate-as-pure",
+  "version": "7.0.0-beta.1",
+  "description": "Helper function to annotate paths and nodes with #__PURE__ comment",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-helper-annotate-as-pure",
+  "license": "MIT",
+  "main": "lib/index.js",
+  "dependencies": {
+    "babel-types": "7.0.0-beta.1"
+  }
+}
diff --git a/packages/babel-helper-annotate-as-pure/src/index.js b/packages/babel-helper-annotate-as-pure/src/index.js
new file mode 100644
index 0000000000..5c46e93f99
--- /dev/null
+++ b/packages/babel-helper-annotate-as-pure/src/index.js
@@ -0,0 +1,19 @@
+import * as t from "babel-types";
+
+const PURE_ANNOTATION = "#__PURE__";
+
+const isPureAnnotated = node => {
+  const { leadingComments } = node;
+  if (leadingComments === undefined) {
+    return false;
+  }
+  return leadingComments.some(comment => /[@#]__PURE__/.test(comment.value));
+};
+
+export default function annotateAsPure(pathOrNode) {
+  const node = pathOrNode.node || pathOrNode;
+  if (isPureAnnotated(node)) {
+    return;
+  }
+  t.addComment(node, "leading", PURE_ANNOTATION);
+}
diff --git a/packages/babel-plugin-transform-es2015-classes/package.json b/packages/babel-plugin-transform-es2015-classes/package.json
index f37bf66fa1..e477828378 100644
--- a/packages/babel-plugin-transform-es2015-classes/package.json
+++ b/packages/babel-plugin-transform-es2015-classes/package.json
@@ -6,6 +6,7 @@
   "license": "MIT",
   "main": "lib/index.js",
   "dependencies": {
+    "babel-helper-annotate-as-pure": "7.0.0-beta.1",
     "babel-helper-define-map": "7.0.0-beta.1",
     "babel-helper-function-name": "7.0.0-beta.1",
     "babel-helper-optimise-call-expression": "7.0.0-beta.1",
diff --git a/packages/babel-plugin-transform-es2015-classes/src/index.js b/packages/babel-plugin-transform-es2015-classes/src/index.js
index 6bdac143f9..125be035fe 100644
--- a/packages/babel-plugin-transform-es2015-classes/src/index.js
+++ b/packages/babel-plugin-transform-es2015-classes/src/index.js
@@ -1,9 +1,8 @@
 import LooseTransformer from "./loose";
 import VanillaTransformer from "./vanilla";
+import annotateAsPure from "babel-helper-annotate-as-pure";
 import nameFunction from "babel-helper-function-name";
 
-const PURE_ANNOTATION = "#__PURE__";
-
 export default function({ types: t }) {
   // todo: investigate traversal requeueing
   const VISITED = Symbol();
@@ -57,7 +56,7 @@ export default function({ types: t }) {
         path.replaceWith(new Constructor(path, state.file).run());
 
         if (path.isCallExpression()) {
-          path.addComment("leading", PURE_ANNOTATION);
+          annotateAsPure(path);
           if (path.get("callee").isArrowFunctionExpression()) {
             path.get("callee").arrowFunctionToExpression();
           }
diff --git a/packages/babel-traverse/src/path/comments.js b/packages/babel-traverse/src/path/comments.js
index 909ea43015..38aeaa66f5 100644
--- a/packages/babel-traverse/src/path/comments.js
+++ b/packages/babel-traverse/src/path/comments.js
@@ -1,4 +1,5 @@
 // This file contains methods responsible for dealing with comments.
+import * as t from "babel-types";
 
 /**
  * Share comments amongst siblings.
@@ -27,13 +28,8 @@ export function shareCommentsWithSiblings() {
   }
 }
 
-export function addComment(type, content, line?) {
-  this.addComments(type, [
-    {
-      type: line ? "CommentLine" : "CommentBlock",
-      value: content,
-    },
-  ]);
+export function addComment(type: string, content: string, line?: boolean) {
+  t.addComment(this.node, type, content, line);
 }
 
 /**
@@ -41,20 +37,5 @@ export function addComment(type, content, line?) {
  */
 
 export function addComments(type: string, comments: Array) {
-  if (!comments) return;
-
-  const node = this.node;
-  if (!node) return;
-
-  const key = `${type}Comments`;
-
-  if (node[key]) {
-    if (type === "leading") {
-      node[key] = comments.concat(node[key]);
-    } else {
-      node[key] = node[key].concat(comments);
-    }
-  } else {
-    node[key] = comments;
-  }
+  t.addComments(this.node, type, comments);
 }
diff --git a/packages/babel-types/src/index.js b/packages/babel-types/src/index.js
index 2e5fa0797d..72bdb99560 100644
--- a/packages/babel-types/src/index.js
+++ b/packages/babel-types/src/index.js
@@ -399,6 +399,49 @@ export function buildMatchMemberExpression(
   };
 }
 
+/**
+ * Add comment of certain type to a node.
+ */
+
+export function addComment(
+  node: Object,
+  type: string,
+  content: string,
+  line?: boolean,
+): Object {
+  addComments(node, type, [
+    {
+      type: line ? "CommentLine" : "CommentBlock",
+      value: content,
+    },
+  ]);
+}
+
+/**
+ * Add comments of certain type to a node.
+ */
+
+export function addComments(
+  node: Object,
+  type: string,
+  comments: Array,
+): Object {
+  if (!comments || !node) return;
+
+  const key = `${type}Comments`;
+
+  if (node[key]) {
+    if (type === "leading") {
+      node[key] = comments.concat(node[key]);
+    } else {
+      node[key] = node[key].concat(comments);
+    }
+  } else {
+    node[key] = comments;
+  }
+  return node;
+}
+
 /**
  * Remove comment properties from a node.
  */