Topography is a fundamental factor influencing the emplacement of lava flows. We assess the impact of topographic resolution on the thermorheological PyFLOWGO model, specifically with digital elevation model (DEM) resolutions commonly available for Earth and other planetary bodies where flow modeling is relevant. We examined PyFLOWGO output parameters (e.g., channel length, core temperature, and flow velocity) to assess model sensitivity to topography in order to document model uncertainties and optimize future application. This study uses rheologic and topographic data from the Tolbachik, Russia 2012–2013 eruption as model constraints. Using moderate to lower resolution topographic data overestimates the channelized flow length by up to 35% due to differences in the distribution of slopes topographic variability at different resolutions and resulting effects on the modeled lava velocity down channel. Determining the impact of topography on thermorheological lava flow models such as PyFLOWGO is important to correctly interpret the results for channelized flows.