diff --git a/src/Form/JobForm.php b/src/Form/JobForm.php
index 7eba8a6..04b1dfc 100644
--- a/src/Form/JobForm.php
+++ b/src/Form/JobForm.php
@@ -7,9 +7,9 @@
 
 namespace Drupal\tmgmt\Form;
 
-use Drupal\Component\Utility\Html;
 use Drupal\Core\Ajax\AjaxResponse;
 use Drupal\Core\Ajax\ReplaceCommand;
+use Drupal\Core\Ajax\InsertCommand;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Url;
@@ -381,6 +381,14 @@ class JobForm extends TmgmtFormBase {
     }
 
     $form['#attached']['library'][] = 'tmgmt/admin';
+
+    // Checkout whether given source already has items in translation.
+    $num_of_existing_items = count($this->checkoutExistingItems());
+    if ($num_of_existing_items) {
+      drupal_set_message(\Drupal::translation()->formatPlural($num_of_existing_items, 'Already exist item in translation.', 'Already exist @count items in translation.'), 'warning');
+    }
+
+
     return $form;
   }
 
@@ -572,10 +580,14 @@ class JobForm extends TmgmtFormBase {
    * target / source language dropdowns.
    */
   public function ajaxLanguageSelect(array $form, FormStateInterface $form_state) {
+    $number_of_existing_items = count($this->checkoutExistingItems());
     $replace = $form_state->getUserInput()['_triggering_element_name'] == 'source_language' ? 'target_language' : 'source_language';
     $response = new AjaxResponse();
     $response->addCommand(new ReplaceCommand('#tmgmt-ui-translator-wrapper', $form['translator_wrapper']));
     $response->addCommand(new ReplaceCommand('#tmgmt-ui-' . str_replace('_', '-', $replace), $form['info'][$replace]));
+    if ($number_of_existing_items) {
+      $response->addCommand(new InsertCommand('.region-highlighted', '<div class="messages messages--warning">' . \Drupal::translation()->formatPlural($number_of_existing_items, 'Already exist item in translation.', 'Already exist @count items in translation.') . '</div>'));
+    }
     return $response;
   }
 
@@ -587,6 +599,25 @@ class JobForm extends TmgmtFormBase {
   }
 
   /**
+   * Helper function for retrieving number of existing items.
+   */
+  function checkoutExistingItems() {
+    $job = $this->entity;
+    $items = $job->getItems();
+    $latest_items_of_chosen_source = array();
+    $ids_of_existing_items = array();
+    foreach ($items as $item) {
+      $latest_items_of_chosen_source[$item->id()] = tmgmt_job_item_load_latest($item->getPlugin(), $item->getItemType(), $item->getItemId(), $job->getSourceLangcode());
+    }
+    foreach ($latest_items_of_chosen_source as $key => $item) {
+      if (array_key_exists($job->getTargetLangcode(), $item)) {
+        $ids_of_existing_items[] = $key;
+      }
+    }
+    return $ids_of_existing_items;
+  }
+
+  /**
    * Adds selected suggestions to the job.
    */
   function addSuggestionsSubmit(array $form, FormStateInterface $form_state) {