diff --git a/src/engine/blocks.js b/src/engine/blocks.js
index e73f4b27..f718aa61 100644
--- a/src/engine/blocks.js
+++ b/src/engine/blocks.js
@@ -247,7 +247,7 @@ class Blocks {
     // ---------------------------------------------------------------------
 
     /**
-     * Create event listener for blocks and variables. Handles validation and
+     * Create event listener for blocks, variables, and comments. Handles validation and
      * serves as a generic adapter between the blocks, variables, and the
      * runtime interface.
      * @param {object} e Blockly "block" or "variable" event
@@ -256,7 +256,8 @@ class Blocks {
     blocklyListen (e, optRuntime) {
         // Validate event
         if (typeof e !== 'object') return;
-        if (typeof e.blockId !== 'string' && typeof e.varId !== 'string') {
+        if (typeof e.blockId !== 'string' && typeof e.varId !== 'string' &&
+            typeof e.commentId !== 'string') {
             return;
         }
         const stage = optRuntime.getTargetForStage();
@@ -356,6 +357,74 @@ class Blocks {
         case 'var_delete':
             stage.deleteVariable(e.varId);
             break;
+        case 'comment_create':
+            if (optRuntime.getEditingTarget()) {
+                const currTarget = optRuntime.getEditingTarget();
+                currTarget.createComment(e.commentId, e.blockId, e.text,
+                    e.xy.x, e.xy.y, e.width, e.height, e.minimized);
+            }
+            break;
+        case 'comment_change':
+            if (optRuntime) {
+                const currTarget = optRuntime.getEditingTarget();
+                if (!currTarget.comments.hasOwnProperty(e.commentId)) {
+                    log.warn(`Cannot change comment with id ${e.commentId} because it does not exist.`);
+                    return;
+                }
+                const comment = currTarget.comments[e.commentId];
+                const change = e.newContents_;
+                if (typeof change === 'object') {
+                    if (change.hasOwnProperty('minimized')) {
+                        comment.minimized = change.minimized;
+                        break;
+                    } else if (change.hasOwnProperty('width') && change.hasOwnProperty('height')){
+                        comment.width = change.width;
+                        comment.height = change.height;
+                        break;
+                    }
+                } else if (typeof change === 'string') {
+                    comment.text = change;
+                    break;
+                }
+                log.warn(`Unrecognized comment change: ${
+                    JSON.stringify(change)} for comment with id: ${e.commentId}.`);
+                return;
+            }
+            break;
+        case 'comment_move':
+            if (optRuntime) {
+                const currTarget = optRuntime.getEditingTarget();
+                if (!currTarget.comments.hasOwnProperty(e.commentId)) {
+                    log.warn(`Cannot change comment with id ${e.commentId} because it does not exist.`);
+                    return;
+                }
+                const comment = currTarget.comments[e.commentId];
+                const newCoord = e.newCoordinate_;
+                comment.x = Math.floor(newCoord.x);
+                comment.y = Math.floor(newCoord.y);
+            }
+            break;
+        case 'comment_delete':
+            if (optRuntime) {
+                const currTarget = optRuntime.getEditingTarget();
+                if (!currTarget.comments.hasOwnProperty(e.commentId)) {
+                    // If we're in this state, we have probably received
+                    // a delete event from a workspace that we switched from
+                    // (e.g. a delete event for a comment on sprite a's workspace
+                    // when switching from sprite a to sprite b)
+                    return;
+                }
+                delete currTarget.comments[e.commentId];
+                if (e.blockId) {
+                    const block = currTarget.blocks.getBlock(e.blockId);
+                    if (!block) {
+                        log.warn(`Could not find block referenced by comment with id: ${e.commentId}`);
+                        return;
+                    }
+                    delete block.comment;
+                }
+            }
+            break;
         }
     }
 
diff --git a/src/engine/target.js b/src/engine/target.js
index 22325422..3faab5d4 100644
--- a/src/engine/target.js
+++ b/src/engine/target.js
@@ -2,6 +2,7 @@ const EventEmitter = require('events');
 
 const Blocks = require('./blocks');
 const Variable = require('../engine/variable');
+const Comment = require('../engine/comment');
 const uid = require('../util/uid');
 const {Map} = require('immutable');
 const log = require('../util/log');
@@ -190,6 +191,30 @@ class Target extends EventEmitter {
         }
     }
 
+    /**
+     * Creates a comment with the given properties.
+     * @param {string} id Id of the comment.
+     * @param {string} blockId Optional id of the block the comment is attached
+     * to if it is a block comment.
+     * @param {string} text The text the comment contains.
+     * @param {number} x The x coordinate of the comment on the workspace.
+     * @param {number} y The y coordinate of the comment on the workspace.
+     * @param {number} width The width of the comment when it is full size
+     * @param {number} height The height of the comment when it is full size
+     * @param {boolean} minimized Whether the comment is minimized.
+     */
+    createComment (id, blockId, text, x, y, width, height, minimized) {
+        if (!this.comments.hasOwnProperty(id)) {
+            const newComment = new Comment(id, text, x, y,
+                width, height, minimized);
+            if (blockId) {
+                newComment.blockId = blockId;
+                this.blocks.getBlock(blockId).comment = id;
+            }
+            this.comments[id] = newComment;
+        }
+    }
+
     /**
      * Renames the variable with the given id to newName.
      * @param {string} id Id of renamed variable.