Benefitting from the higher quantum efficiency and sensitivity compared with the front-side illumination (FSI) CMOS image sensors (CISs), backside illumination (BSI) CMOS image sensors tend to replace CCDs and FSI CISs for space applications. However, the radiation damage effects and mechanisms of BSI CISs in the radiation environment are not well understood. We provide radiation effects due to 3 MeV proton irradiations of BSI CISs dedicated to imaging by the analyses of mean dark current increase, dark current nonuniformity and full well capacity in pixel arrays and isolated photodiodes. Additionally, the present annealing certifies the radiation-induced defects, which are responsible for the parameter degradations in BSI CISs.