diff --git a/rest_framework_json_api/utils.py b/rest_framework_json_api/utils.py
index e37f4110..24adda77 100644
--- a/rest_framework_json_api/utils.py
+++ b/rest_framework_json_api/utils.py
@@ -228,8 +228,12 @@ def extract_relationships(fields, resource, resource_instance):
         if not isinstance(field, (RelatedField, ManyRelatedField, BaseSerializer)):
             continue
 
+        try:
+            relation_instance_or_manager = getattr(resource_instance, field_name)
+        except AttributeError: # Skip fields defined on the serializer that don't correspond to a field on the model
+            continue
+
         relation_type = get_related_resource_type(field)
-        relation_instance_or_manager = getattr(resource_instance, field_name)
 
         if isinstance(field, HyperlinkedIdentityField):
             # special case for HyperlinkedIdentityField