The Guadalupe Bass (Microperus treculii, hereafter GB) is a vulnerable endemic species that is designated as the state fish of Texas. GB are threatened by urbanization and climate change and these thermal effects could alter GB performance. Thus, there is a need to enhance physiological knowledge regarding thermal effects on GB physiology and behavior to enhance conservation efforts. We fill knowledge gaps by projecting growth of GB using a bioenergetic model (BEM) and exploring the effects of urbanization and climate change on GB performance. Our first objective uses temperature and mass dependent maximum consumption (Cmax) and routine respiration (Rrout) experiments to parameterize a BEM. We quantified Rrout using intermittent flow respirometry and Cmax by feeding GB ad libitum rations of prey across biologically realistic temperatures and body sizes. The optimal temperature for performance was 29.7°C. Our second objective was to project growth of age-1 GB spanning one year and validate the projections using length-at-age data for GB. Validated growth was simulated by selecting intrinsic parameters for proportion of consumption (CP) and activity level (ACT) using Monte Carlo resampling. Our third objective was to simulate growth and survival along an existing urbanization gradient and under scenarios of future climate change. We used temperature data from 68 field monitoring stations distributed throughout the GB native range in Texas. Contemporary end-of-year mass was 75.9 g in rural streams but increased to 82.9 g in urban streams, ostensibly due to increased stream temperatures caused by the urban heat island effect. Future growth under climate change (+2°C) increased to 126.1 g in rural streams, likely due to temperatures approaching the thermal optimum (29.7°C). By developing a BEM for GB, we can understand the physiological effects of urbanization and climate change on GB performance allowing managers to take reactive and proactive measures to conserve GB.