Current standards establish methods for seismic assessment and objectives for retrofit of existing building structures and provide guidance for fiber-reinforced polymer (FRP)-based seismic retrofit measures for existing reinforced concrete (RC) structures. However, there is no agreed-upon methodology for assessing—and therefore establishing—the efficacy of an FRP retrofit. Similarly, as FRP retrofits are becoming common, there arises a need to assess FRP-retrofitted concrete members and structures for their subsequent postretrofit performance. In this paper, a data-driven approach to determining modeling parameters for FRP-retrofitted RC columns consistent with current standards is demonstrated and parameters for flexure-dominated column behavior are proposed. A refined backbone curve is proposed for FRP-retrofitted columns in which an incremental rotation capacity accounting for the improved behavior of the retrofitted column is prescribed. Modeling parameters for flexure-dominated columns are proposed.