diff --git a/CRM/Contact/BAO/Relationship.php b/CRM/Contact/BAO/Relationship.php
index c942c3f7a890..cde90f8bc056 100644
--- a/CRM/Contact/BAO/Relationship.php
+++ b/CRM/Contact/BAO/Relationship.php
@@ -120,7 +120,7 @@ public static function createMultiple($params, $primaryContactLetter) {
     foreach ($secondaryContactIDs as $secondaryContactID) {
       try {
         $params['contact_id_' . $secondaryContactLetter] = $secondaryContactID;
-        $relationship = civicrm_api3('relationship', 'create', $params);
+        $relationship = \Civi\Api4\Relationship::create(FALSE)->setValues($params)->execute()->first();
         $relationshipIDs[] = $relationship['id'];
         $valid++;
       }
@@ -1774,10 +1774,11 @@ public static function disableExpiredRelationships() {
    * @throws \CRM_Core_Exception
    */
   public static function membershipTypeToRelationshipTypes(&$params, $direction = NULL) {
-    $membershipType = civicrm_api3('membership_type', 'getsingle', [
-      'id' => $params['membership_type_id'],
-      'return' => 'relationship_type_id, relationship_direction',
-    ]);
+    $membershipType = \Civi\Api4\MembershipType::get(FALSE)
+      ->addSelect('relationship_type_id', 'relationship_direction')
+      ->addWhere('id', '=', $params['membership_type_id'])
+      ->execute()
+      ->first();
     $relationshipTypes = $membershipType['relationship_type_id'];
     if (empty($relationshipTypes)) {
       return NULL;
@@ -2047,7 +2048,7 @@ public static function buildOptions($fieldName, $context = NULL, $props = []) {
   public static function isCurrentEmployerNeedingToBeCleared($params, $relationshipId, $updatedRelTypeID = NULL) {
     $existingTypeID = (int) CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Relationship', $relationshipId, 'relationship_type_id');
     $updatedRelTypeID = $updatedRelTypeID ?: $existingTypeID;
-    $currentEmployerID = (int) civicrm_api3('Contact', 'getvalue', ['return' => 'current_employer_id', 'id' => $params['contact_id_a']]);
+    $currentEmployerID = (int) \Civi\Api4\Contact::get(FALSE)->addSelect('current_employer_id')->addWhere('id', '=', $params['contact_id_a'])->execute()->first()['current_employer_id'];
 
     if ($currentEmployerID !== (int) $params['contact_id_b'] || !self::isRelationshipTypeCurrentEmployer($existingTypeID)) {
       return FALSE;
@@ -2062,13 +2063,7 @@ public static function isCurrentEmployerNeedingToBeCleared($params, $relationshi
       || ((isset($params['is_active']) && empty($params['is_active'])))
       || $existingTypeID != $updatedRelTypeID) {
       // If there are no other active employer relationships between the same 2 contacts...
-      if (!civicrm_api3('Relationship', 'getcount', [
-        'is_active' => 1,
-        'relationship_type_id' => $existingTypeID,
-        'id' => ['<>' => $params['id']],
-        'contact_id_a' => $params['contact_id_a'],
-        'contact_id_b' => $params['contact_id_b'],
-      ])) {
+      if (!\Civi\Api4\Relationship::get(FALSE)->selectRowCount()->addWhere('is_active', '=', TRUE)->addWhere('relationship_type_id', '=', $existingTypeID)->addWhere('id', '!=', $params['id'])->addWhere('contact_id_a', '=', $params['contact_id_a'])->addWhere('contact_id_b', '=', $params['contact_id_b'])->execute()->count()) {
         return TRUE;
       }
     }