This paper proposes a nonlocal filter variant that replaces the conventional static search window of nonlocal InSAR filters with an adaptive region growing based search window. The region growing approach has the allure that it preselects only similar pixels for the averaging process and that it may find a larger number of statistically homogeneous pixels than a traditional, fixed search window. A Monte-Carlo simulation shows the possible benefits that could be realized with the region growing approach for InSAR filtering. The proposed method is also experimentally evaluated for rural and urban test sites.