 <p>Assuming that identifyArrayCollection is an ArrayCollection containing some Objects and speedsArrayCollection is an ArrayCollection defined as variable of the Object type that are contained in the identifyArrayCollection </p> <p>you should do:</p> <pre><code>for (var x:Number = 0; x &lt; identifyArrayCollection.length; x++) { identifyArrayCollection.getItemAt(x).speedsArrayCollection.addItem(speedsObj); } </code></pre>