diff --git a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
index 2d5bbe215..afec2e03c 100644
--- a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
+++ b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
@@ -223,8 +223,8 @@ class GridFieldAddExistingAutocompleter implements GridField_HTMLProvider, GridF
      */
     public function doSearch($gridField, $request)
     {
+        $searchStr = $request->getVar('gridfield_relationsearch');
         $dataClass = $gridField->getModelClass();
-        $allList = $this->searchList ? $this->searchList : DataList::create($dataClass);
 
         $searchFields = ($this->getSearchFields())
             ? $this->getSearchFields()
@@ -241,12 +241,22 @@ class GridFieldAddExistingAutocompleter implements GridField_HTMLProvider, GridF
         $params = [];
         foreach ($searchFields as $searchField) {
             $name = (strpos($searchField, ':') !== false) ? $searchField : "$searchField:StartsWith";
-            $params[$name] = $request->getVar('gridfield_relationsearch');
+            $params[$name] = $searchStr;
         }
-        $results = $allList
+
+        $results = null;
+        if ($this->searchList) {
+            // Assume custom sorting, don't apply default sorting
+            $results = $this->searchList;
+        } else {
+            $results = DataList::create($dataClass)
+                ->sort(strtok($searchFields[0], ':'), 'ASC');
+        }
+
+        // Apply baseline filtering and limits which should hold regardless of any customisations
+        $results = $results
             ->subtract($gridField->getList())
             ->filterAny($params)
-            ->sort(strtok($searchFields[0], ':'), 'ASC')
             ->limit($this->getResultsLimit());
 
         $json = [];
diff --git a/tests/php/Forms/GridField/GridFieldAddExistingAutocompleterTest.php b/tests/php/Forms/GridField/GridFieldAddExistingAutocompleterTest.php
index 7c1aca2c6..89b790f7f 100644
--- a/tests/php/Forms/GridField/GridFieldAddExistingAutocompleterTest.php
+++ b/tests/php/Forms/GridField/GridFieldAddExistingAutocompleterTest.php
@@ -2,10 +2,14 @@
 
 namespace SilverStripe\Forms\Tests\GridField;
 
+use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Core\Convert;
 use SilverStripe\Dev\CSSContentParser;
 use SilverStripe\Dev\FunctionalTest;
+use SilverStripe\Forms\GridField\GridField;
 use SilverStripe\Forms\GridField\GridFieldAddExistingAutocompleter;
+use SilverStripe\Forms\GridField\GridFieldConfig;
+use SilverStripe\Forms\GridField\GridFieldDataColumns;
 use SilverStripe\Forms\Tests\GridField\GridFieldAddExistingAutocompleterTest\TestController;
 use SilverStripe\Forms\Tests\GridField\GridFieldTest\Cheerleader;
 use SilverStripe\Forms\Tests\GridField\GridFieldTest\Permissions;
@@ -127,4 +131,54 @@ class GridFieldAddExistingAutocompleterTest extends FunctionalTest
             new ArrayList([$team1, $team2])
         );
     }
+
+    public function testRetainsCustomSort()
+    {
+        $component = new GridFieldAddExistingAutocompleter($targetFragment = 'before', ['Test']);
+        $component->setSearchFields(['Name']);
+
+        $grid = $this->getGridFieldForComponent($component);
+        $grid->setList(Team::get()->filter('Name', 'force-empty-list'));
+
+        $component->setSearchList(Team::get());
+        $request = new HTTPRequest('GET', '', ['gridfield_relationsearch' => 'Team']);
+        $response = $component->doSearch($grid, $request);
+        $this->assertFalse($response->isError());
+        $result = json_decode($response->getBody(), true);
+        $this->assertEquals(
+            ['Team 1', 'Team 2', 'Team 3', 'Team 4'],
+            array_map(
+                function ($item) {
+                    return $item['label'];
+                },
+                $result
+            )
+        );
+
+        $component->setSearchList(Team::get()->sort('Name', 'DESC'));
+        $request = new HTTPRequest('GET', '', ['gridfield_relationsearch' => 'Team']);
+        $response = $component->doSearch($grid, $request);
+        $this->assertFalse($response->isError());
+        $result = json_decode($response->getBody(), true);
+        $this->assertEquals(
+            ['Team 4', 'Team 3', 'Team 2', 'Team 1'],
+            array_map(
+                function ($item) {
+                    return $item['label'];
+                },
+                $result
+            )
+        );
+    }
+
+    protected function getGridFieldForComponent($component)
+    {
+        $config = GridFieldConfig::create()->addComponents(
+            $component,
+            new GridFieldDataColumns()
+        );
+
+        return (new GridField('testfield', 'testfield'))
+            ->setConfig($config);
+    }
 }