 <p>For a repeater field of act you have to use the field_key not the name. This was the answer to my question.</p> <pre><code>$startlocation = array(); $startlocation[] = array( 'lat' =&gt; $route['startingSpot']['location']['lat'], 'lng' =&gt; $route['startingSpot']['location']['lng'], 'description' =&gt; $route['startingSpot']['nl'], 'direction' =&gt; $route['startingSpot']['direction'] ); update_field('field_dhjawhdwkwkhd', $startlocation, $post_id ); </code></pre>