The impact of climate change in the habitat suitability for the adult brown trout (Salmo trutta L.) was studied in a segment of the Cabriel River (Iberian Peninsula). The Temez precipitation–runoff model calibrated for the 1960-2000 period (NSE: 0.72) was used to simulate two short-term scenarios under the new Representative Concentration Pathways (RCP 2.6 and 8.5). An ensemble of five strongly regularized machine learning techniques (boosted regression trees, generalized additive models, multilayer perceptron ensembles, fuzzy rule base models and support vector machines) was used to model the microhabitat suitability (depth, velocity and substrate) during summertime and to assess several flows simulated with River-2D. The hydrological simulation and habitat assessment were combined to infer the habitat duration curves (HDC) under historical conditions and the climate change scenarios. An increment of extreme flow events, either lower or higher, was observed under the two scenarios. The five techniques converged on the modelled suitability (TSS: 0.46±0.05) thus, adult brown trout selected relatively high flow velocity, large depth and coarse substrate. The five HDC indicated a significant increment on the frequency of low-habitat events. The river segment proved unable to buffer the negative effect of flow reductions then, an increment of habitat competition in this territorial species is likely to occur. Finally, the results suggested the extirpation of the species from the study site during short time spans. This piece of research represents a valuable example of the ultimate impacts of climate change in adult brown trout.