Abstract: Based on a set of twenty-first-century climate change projections by a regional climate model (RegCM4) at a 25-km grid spacing driven by five global models, future climate change over Xinjiang in Northwest China under the middle and high representative concentration pathways of 4.5 and 8.5 (RCP4.5 and RCP8.5) is investigated. Results show the multi-RegCM4 ensemble (ensR) clearly determines both the spatial distributions and the amounts of mean temperature and precipitation, along with extreme temperature and precipitation. In the future, the temperature and precipitation over Xinjiang are projected to rise or increase continuously, especially under RCP8.5 compared with RCP4.5. Moreover, by the end of the twenty-first century under RCP8.5, the regional mean increases in annual temperature and precipitation will be as 4.9°C and 28% (102 mm), respectively. Increases of temperature and precipitation extremes are also reported as measured by different indices, indicating more heat waves, less cold spells, and more extreme precipitation in the future. Specifically, for temperature, greater increase of annual minimum of daily minimum temperature (TNn) is found compared to annual maximum of daily maximum temperature (TXx). By the end of the twenty-first century under RCP8.5, the increase of regional mean TXx and TNn over Xinjiang will be 4.9°C and 5.8°C, respectively. As for extreme precipitation indices, an increase of RX1day by 29% (5 mm) and a decrease of CDD by 10 days are found. The change of snow cover shows spatial differences, with a general decrease except a large percentage increase in the western Tarim Basin. A 13% reduction is reported for the regional mean snow coverage at the end of the twenty-first century under RCP8.5. The total runoff and soil moisture are projected to increase; however, more hydrological droughts in northern Xinjiang are projected to occur. The ensR show consistencies among the ensemble members, but there exist differences concerning the change of amount and the sign in some cases. Overall, considering the analyzed variables, a “warmer and more humid” tendency of climate as observed in the late decades will be expected in Xinjiang in the future. However, this may not change the fact of the dominance of arid and semiarid climate over the region. In addition, hydrological droughts are also projected to increase in the future. Thus, high attention still needs to be paid for the availability and risks on water resources over the region.