diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65a67347..0c18dd1c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Fix incompatibility of `multiple` dropdowns with `massiveaction`
 
+### Added
+- Add `replace` and `add` options in massive action for the multiple dropdowns fields
+
 ## [1.21.22] - 2025-05-28
 
 ### Fixed
diff --git a/hook.php b/hook.php
index f6fadaa9..9f762dcb 100644
--- a/hook.php
+++ b/hook.php
@@ -206,6 +206,16 @@ function plugin_fields_MassiveActionsFieldsDisplay($options = [])
     $itemtypes = PluginFieldsContainer::getEntries('all');
 
     if (in_array($options['itemtype'], $itemtypes)) {
+        if ($options['options']['is_multiple']) {
+            Dropdown::showFromArray(
+                'multiple_dropdown_action',
+                [
+                    'assign' => __('Assign'),
+                    'append' => __('Add'),
+                ],
+            );
+        }
+
         PluginFieldsField::showSingle($options['itemtype'], $options['options'], true);
 
         return true;
diff --git a/inc/container.class.php b/inc/container.class.php
index 8d5c3fe4..132f5a2d 100644
--- a/inc/container.class.php
+++ b/inc/container.class.php
@@ -1211,6 +1211,17 @@ public function updateFieldsValues($data, $itemtype, $massiveaction = false)
             return false;
         }
 
+        //Get object classname
+        $container_obj = new PluginFieldsContainer();
+        $container_obj->getFromDB($data['plugin_fields_containers_id']);
+
+        $items_id  = $data['items_id'];
+        $classname = self::getClassname($itemtype, $container_obj->fields['name']);
+
+        $obj = new $classname();
+
+        $exist = $obj->getFromDBByCrit(['items_id' => $items_id]);
+
         // Convert "multiple" values into a JSON string
         $multiple_fields_iterator = $DB->request([
             'FROM'  => PluginFieldsField::getTable(),
@@ -1226,20 +1237,20 @@ public function updateFieldsValues($data, $itemtype, $massiveaction = false)
                 $field_name = 'plugin_fields_' . $field_data['name'] . 'dropdowns_id';
             }
             if (array_key_exists($field_name, $data)) {
-                $data[$field_name] = json_encode($data[$field_name]);
+                if ($data['multiple_dropdown_action'] === 'append' && $exist) {
+                    // Add new values to existing ones
+                    $existing_values = json_decode($obj->fields[$field_name] ?? '[]', true);
+                    $new_values      = is_array($data[$field_name]) ? $data[$field_name] : [$data[$field_name]];
+                    $data[$field_name] = json_encode(array_unique(array_merge($existing_values, $new_values)));
+                } else {
+                    $data[$field_name] = json_encode($data[$field_name]);
+                }
             } elseif (array_key_exists('_' . $field_name . '_defined', $data)) {
                 $data[$field_name] = json_encode([]);
             }
         }
 
-        $container_obj = new PluginFieldsContainer();
-        $container_obj->getFromDB($data['plugin_fields_containers_id']);
-
-        $items_id  = $data['items_id'];
-        $classname = self::getClassname($itemtype, $container_obj->fields['name']);
-
-        $obj = new $classname();
-        if ($obj->getFromDBByCrit(['items_id' => $items_id]) === false) {
+        if ($exist === false) {
             // add fields data
             $obj->add($data);
         } else {
@@ -1729,6 +1740,7 @@ public static function preItem(CommonDBTM $item)
 
                 return false;
             }
+
             $item->input['_plugin_fields_data'] = $data;
 
             return true;
@@ -1819,6 +1831,7 @@ private static function populateData($c_id, CommonDBTM $item)
                 // ex my_dom[]
                 //in these conditions, the input is never sent by the browser
                 if ($field['multiple']) {
+                    $data['multiple_dropdown_action'] = $_POST['multiple_dropdown_action'];
                     //handle multi dropdown field
                     if ($field['type'] == 'dropdown') {
                         $multiple_key         = sprintf('plugin_fields_%sdropdowns_id', $field['name']);
@@ -1960,6 +1973,10 @@ public static function getAddSearchOptions($itemtype, $containers_id = false)
             $opt[$i]['pfields_type']      = $data['type'];
             $opt[$i]['pfields_fields_id'] = $data['field_id'];
 
+            if ($data['type'] === 'dropdown') {
+                $opt[$i]['is_multiple'] = $data['multiple'];
+            }
+
             if ($data['is_readonly']) {
                 $opt[$i]['massiveaction'] = false;
             }