Total ionizing dose effects are studied on a radiation hardened by design (RHBD) 256×256 -pixel CMOS image sensor (CIS) demonstrator developed for ITER remote handling by using X- and γ -ray irradiations. The (color) imaging capabilities of the RHBD CIS are demonstrated up to 10 MGy (SiO2), 1 Grad (SiO2), validating the radiation hardness of most of the designed integrated circuit. No significant sensitivity (i.e., responsivity and color filter transmittance) or readout noise degradation is observed. The proposed readout chain architecture allows achieving a maximum output voltage swing larger than 1 V at 10 MGy (SiO2). The influence of several pixel layout (the gate oxide thickness, the gate overlap distance, and the use of an in-pixel P+ ring) and manufacturing process parameters (photodiode doping profile and process variation) on the radiation-induced dark current increase is studied. The nature of the dark current draining mechanism used to cancel most of the radiation-induced degradation is also discussed and clarified.