diff --git a/internal/gengapic/genrest.go b/internal/gengapic/genrest.go
index 5a2569ea1..6fbb96c10 100644
--- a/internal/gengapic/genrest.go
+++ b/internal/gengapic/genrest.go
@@ -420,6 +420,7 @@ func (g *generator) generateQueryString(m *descriptor.MethodDescriptorProto) {
 		singularPrimitive := field.GetType() != fieldTypeMessage &&
 			field.GetType() != fieldTypeBytes &&
 			field.GetLabel() != fieldLabelRepeated
+		key := lowerFirst(snakeToCamel(path))
 
 		var paramAdd string
 		// Handle well known protobuf types with special JSON encodings.
@@ -435,10 +436,10 @@ func (g *generator) generateQueryString(m *descriptor.MethodDescriptorProto) {
 				b.WriteString("  return nil, err\n")
 			}
 			b.WriteString("}\n")
-			b.WriteString(fmt.Sprintf("params.Add(%q, string(%s))", lowerFirst(snakeToCamel(path)), field.GetJsonName()))
+			b.WriteString(fmt.Sprintf("params.Add(%q, string(%s))", key, field.GetJsonName()))
 			paramAdd = b.String()
 		} else {
-			paramAdd = fmt.Sprintf("params.Add(%q, fmt.Sprintf(%q, req%s))", lowerFirst(snakeToCamel(path)), "%v", accessor)
+			paramAdd = fmt.Sprintf("params.Add(%q, fmt.Sprintf(%q, req%s))", key, "%v", accessor)
 			g.imports[pbinfo.ImportSpec{Path: "fmt"}] = true
 		}
 
@@ -450,8 +451,14 @@ func (g *generator) generateQueryString(m *descriptor.MethodDescriptorProto) {
 		}
 
 		if field.GetLabel() == fieldLabelRepeated {
-			// It's a slice, so check for nil
-			p("if req%s != nil {", accessor)
+			// It's a slice, so check for len > 0, nil slice returns 0.
+			p("if items := req%s; len(items) > 0 {", accessor)
+			b := strings.Builder{}
+			b.WriteString("for _, item := range items {\n")
+			b.WriteString(fmt.Sprintf("  params.Add(%q, fmt.Sprintf(%q, item))\n", key, "%v"))
+			b.WriteString("}")
+			paramAdd = b.String()
+
 		} else if field.GetProto3Optional() {
 			// Split right before the raw access
 			toks := strings.Split(path, ".")
diff --git a/internal/gengapic/genrest_test.go b/internal/gengapic/genrest_test.go
index d2f0a300f..adddf0e0e 100644
--- a/internal/gengapic/genrest_test.go
+++ b/internal/gengapic/genrest_test.go
@@ -499,9 +499,16 @@ func TestGenRestMethod(t *testing.T) {
 		TypeName: proto.String(".google.protobuf.FieldMask"),
 	}
 
+	repeatedPrimField := &descriptor.FieldDescriptorProto{
+		Name:     proto.String("primitives"),
+		Type:     descriptor.FieldDescriptorProto_TYPE_STRING.Enum().Enum(),
+		TypeName: proto.String(foofqn),
+		Label:    descriptor.FieldDescriptorProto_LABEL_REPEATED.Enum(),
+	}
+
 	updateReq := &descriptor.DescriptorProto{
 		Name:  proto.String("UpdateRequest"),
-		Field: []*descriptor.FieldDescriptorProto{fooField, maskField},
+		Field: []*descriptor.FieldDescriptorProto{fooField, maskField, repeatedPrimField},
 	}
 	updateReqFqn := fmt.Sprintf(".%s.UpdateRequest", pkg)
 
diff --git a/internal/gengapic/testdata/rest_UpdateRPC.want b/internal/gengapic/testdata/rest_UpdateRPC.want
index 7d31bdfa9..2236933f9 100644
--- a/internal/gengapic/testdata/rest_UpdateRPC.want
+++ b/internal/gengapic/testdata/rest_UpdateRPC.want
@@ -14,6 +14,11 @@ func (c *fooRESTClient) UpdateRPC(ctx context.Context, req *foopb.UpdateRequest,
 
 	params := url.Values{}
 	params.Add("$alt", "json;enum-encoding=int")
+	if items := req.GetPrimitives(); len(items) > 0 {
+		for _, item := range items {
+		  params.Add("primitives", fmt.Sprintf("%v", item))
+		}
+	}
 	if req.GetUpdateMask() != nil {
 		updateMask, err := protojson.Marshal(req.GetUpdateMask())
 		if err != nil {