Posted this answer in the issue @attiks mentioned as well: The easiest thing to do is to add the states in hook_form_alter() or in hook_form_FORM_ID_alter(). I got Clientside Validation to work on fields within a group, within a field collection. Here's my code: /** * Implements hook_form_FORM_ID_alter(). */ function fgtest_form_article_node_form_alter(&$form, $form_state) { $group = 'group_customgroup'; $collection_bundle = 'field_my_collection'; $fields = array_keys($form[$collection_bundle]['und'][0]['#group_children'], $group); foreach (element_children($form[$collection_bundle]['und']) as $delta) { $collection = &$form[$collection_bundle]['und'][$delta]; foreach ($fields as $field) { $collection[$field]['und'][0]['value']['#states'] = array( 'required' => array( "#edit-field-my-collection-und-{$delta}-field-make-required-und" => array('checked' => TRUE), ), ); } } } And here's my setup: **Node Article:** ![snap1][1] **Field Collection field_my_collection:** ![snap2][2] [1]: https://i.sstatic.net/EGs45.png [2]: https://i.sstatic.net/3S9JI.png