diff --git a/packages/forest_admin_agent/lib/forest_admin_agent/routes/capabilities/collections.rb b/packages/forest_admin_agent/lib/forest_admin_agent/routes/capabilities/collections.rb
index ab61dd770..b9accaad9 100644
--- a/packages/forest_admin_agent/lib/forest_admin_agent/routes/capabilities/collections.rb
+++ b/packages/forest_admin_agent/lib/forest_admin_agent/routes/capabilities/collections.rb
@@ -63,7 +63,8 @@ def handle_request(args = {})
               collections: result,
               nativeQueryConnections: connections,
               agentCapabilities: {
-                canUseProjectionOnGetOne: true
+                canUseProjectionOnGetOne: true,
+                canUseMultipleFieldsProjectionOnRelation: true
               }
             },
             status: 200
diff --git a/packages/forest_admin_agent/lib/forest_admin_agent/utils/query_string_parser.rb b/packages/forest_admin_agent/lib/forest_admin_agent/utils/query_string_parser.rb
index 901c22f2d..16618df5a 100644
--- a/packages/forest_admin_agent/lib/forest_admin_agent/utils/query_string_parser.rb
+++ b/packages/forest_admin_agent/lib/forest_admin_agent/utils/query_string_parser.rb
@@ -63,7 +63,7 @@ def self.add_polymorphic_type_fields(collection, requested_field_names)
       end
 
       def self.build_projection_fields(collection, requested_field_names, args)
-        requested_field_names.map do |field_name|
+        requested_field_names.flat_map do |field_name|
           field = get_field(collection, field_name)
 
           case field.type
@@ -73,7 +73,12 @@ def self.build_projection_fields(collection, requested_field_names, args)
             "#{field_name}:*"
           else
             relation_fields = args.dig(:params, :fields, field_name)
-            "#{field_name}:#{relation_fields}"
+
+            if relation_fields.nil? || relation_fields.empty?
+              "#{field_name}:#{relation_fields}"
+            else
+              relation_fields.split(',').map { |sub_field| "#{field_name}:#{sub_field.strip}" }
+            end
           end
         end
       end
diff --git a/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/capabilities/collections_spec.rb b/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/capabilities/collections_spec.rb
index ec1575cb0..bb64ae66a 100644
--- a/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/capabilities/collections_spec.rb
+++ b/packages/forest_admin_agent/spec/lib/forest_admin_agent/routes/capabilities/collections_spec.rb
@@ -84,7 +84,7 @@ module Capabilities
 
           it 'returns agentCapabilities' do
             expect(result[:content][:agentCapabilities]).to eq(
-              { canUseProjectionOnGetOne: true }
+              { canUseProjectionOnGetOne: true, canUseMultipleFieldsProjectionOnRelation: true }
             )
           end
         end
@@ -131,7 +131,7 @@ module Capabilities
 
           it 'returns agentCapabilities' do
             expect(result[:content][:agentCapabilities]).to eq(
-              { canUseProjectionOnGetOne: true }
+              { canUseProjectionOnGetOne: true, canUseMultipleFieldsProjectionOnRelation: true }
             )
           end
         end
diff --git a/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/query_string_parser_spec.rb b/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/query_string_parser_spec.rb
index 4ab8ca0be..1af986c6f 100644
--- a/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/query_string_parser_spec.rb
+++ b/packages/forest_admin_agent/spec/lib/forest_admin_agent/utils/query_string_parser_spec.rb
@@ -333,6 +333,20 @@ module Utils
           expect(described_class.parse_projection_with_pks(collection,
                                                            args)).to eq(Projection.new(%w[id author:name author:id]))
         end
+
+        it 'supports multiple projected fields on a belongsTo relation' do
+          args = {
+            params: {
+              fields: {
+                'Book' => 'id, author',
+                'author' => 'id,name'
+              }
+            }
+          }
+
+          expect(described_class.parse_projection_with_pks(collection,
+                                                           args)).to eq(Projection.new(%w[id author:id author:name]))
+        end
       end
 
       describe 'parse_pagination' do