diff --git a/src/ORM/ManyManyList.php b/src/ORM/ManyManyList.php
index 9ba18e5ff..5ad69cd8f 100644
--- a/src/ORM/ManyManyList.php
+++ b/src/ORM/ManyManyList.php
@@ -433,6 +433,58 @@ class ManyManyList extends RelationList
         }
     }
 
+    /**
+     * Set the extra field data for a single row of the relationship join
+     * table, given the known child ID.
+     *
+     * @param int $itemID The ID of the child for the relationship
+     * @param array $data The data to set, with field names as keys and values as values
+     * @throws InvalidArgumentException if the $data array is invalid
+     */
+    public function setExtraData(int $itemID, array $data): void
+    {
+        // Don't bother doing anything if we aren't given any data
+        if (empty($data)) {
+            return;
+        }
+
+        // Prepare db manipulation
+        $foreignID = $this->getForeignID();
+        $manipulation = [
+            $this->joinTable => [
+                'command' => 'update',
+                'fields' => [],
+                'where' => [
+                    "\"{$this->joinTable}\".\"{$this->foreignKey}\"" => $foreignID,
+                    "\"{$this->joinTable}\".\"{$this->localKey}\"" => $itemID
+                ],
+            ],
+        ];
+
+        /** @var DBField[] $fieldObjects */
+        $fieldObjects = [];
+        // Write extra field to manipluation in the same way
+        // that DataObject::prepareManipulationTable writes fields
+        foreach ($data as $fieldName => $value) {
+            if (!array_key_exists($fieldName, $this->extraFields)) {
+                throw new InvalidArgumentException("Field '$fieldName' is not defined in many_many_extraFields for this relationship");
+            }
+            $fieldObject = Injector::inst()->create($this->extraFields[$fieldName], $fieldName);
+            // Make sure the field assignment is not an array unless the field allows non-scalar values
+            if (is_array($value) && $fieldObject->scalarValueOnly()) {
+                throw new InvalidArgumentException(
+                    'ManyManyList::setExtraData: parameterised field assignments are disallowed'
+                );
+            }
+            // Set the value into the manipulation
+            $fieldObject->setValue($value);
+            $fieldObject->writeToManipulation($manipulation[$this->joinTable]);
+            $fieldObjects[$fieldName] = $fieldObject;
+        }
+
+        DB::manipulate($manipulation);
+    }
+
     /**
      * Find the extra field data for a single row of the relationship join
      * table, given the known child ID.
diff --git a/tests/php/ORM/ManyManyListTest.php b/tests/php/ORM/ManyManyListTest.php
index e3475ef31..f7b4dd5b5 100644
--- a/tests/php/ORM/ManyManyListTest.php
+++ b/tests/php/ORM/ManyManyListTest.php
@@ -11,7 +11,6 @@ use SilverStripe\ORM\Tests\DataObjectTest\Player;
 use SilverStripe\ORM\Tests\DataObjectTest\Team;
 use SilverStripe\ORM\Tests\ManyManyListTest\ExtraFieldsObject;
 use SilverStripe\ORM\Tests\ManyManyListTest\Product;
-use InvalidArgumentException;
 
 class ManyManyListTest extends SapphireTest
 {
@@ -73,7 +72,7 @@ class ManyManyListTest extends SapphireTest
 
         // the actual test is that this does not generate an error in the sql.
         $obj->Products()->add($product, [
-            'Reference' => 'Foo'
+            'Reference' => 'Foo',
         ]);
 
         $result = $obj->Products()->First();
@@ -81,6 +80,36 @@ class ManyManyListTest extends SapphireTest
         $this->assertEquals('Test Product', $result->Title);
     }
 
+    public function testSetExtraData()
+    {
+        $obj = new ManyManyListTest\ExtraFieldsObject();
+        $obj->write();
+
+        $obj2 = new ManyManyListTest\ExtraFieldsObject();
+        $obj2->write();
+
+        $money = new DBMoney();
+        $money->setAmount(100);
+        $money->setCurrency('USD');
+
+        // Set some data on add
+        $obj->Clients()->add($obj2, [
+            'Worth' => $money,
+            'Reference' => 'Foo',
+        ]);
+        // Change the data afterward
+        $money->setAmount(50);
+        $obj->Clients()->setExtraData($obj2->ID, [
+            'Worth' => $money,
+            'Reference' => 'Bar',
+        ]);
+
+        $result = $obj->Clients()->First();
+        $this->assertEquals('Bar', $result->Reference, 'Basic scalar fields should exist');
+        $this->assertInstanceOf(DBMoney::class, $result->Worth, 'Composite fields should exist on the record');
+        $this->assertEquals(50, $result->Worth->getAmount());
+    }
+
     public function testCreateList()
     {
         $list = ManyManyList::create(