The projected temperature and precipitation change under different emissions scenarios using Coupled Model Intercomparison Project Phase 5 models over the northwestern arid regions of China (NWAC) were analyzed using the ensemble of three high-resolution dynamical downscaling simulations: the simulation of the Regional Climate Model version 4.0 (RegCM4) forced by the Beijing Climate Center Climate System Model version 1.1 (BCC_CSM1.1); the Hadley Centre Global Environmental Model version 3 regional climate model (HadGEM3-RA) forced by the Atmosphere-Ocean coupled HadGEM version 2 (HadGEM2-AO); and the Weather Research and Forecasting (WRF) model forced by the Norwegian community Earth System Model (NorESM1-M). Model validation indicated that the multimodel simulations reproduce the spatial and temporal distribution of temperature and precipitation well. The temperature is projected to increase over NWAC under both the 4.5 and 8.5 Representative Concentration Pathways scenarios (RCP4.5 and RCP8.8, respectively) in the middle of the 21st century, but the warming trend is larger under the RCP8.5 scenario. Precipitation shows a significant increasing trend in spring and winter under both RCP4.5 and RCP8.5; but in summer, precipitation is projected to decrease in the Tarim Basin and Junggar Basin. The regional averaged temperature and precipitation show increasing trends in the future over NWAC; meanwhile, the large variability of the winter mean temperature and precipitation may induce more extreme cold events and intense snowfall events in these regions in the future.