The effect of hydrogen plasma exposure on the deep levels in GaAs grown by the horizontal Bridgman method was studied. After hydrogenation at 250 °C for 3 h, the concentrations of the electron deep levels, such as the EL2 trap (Ec‐0.81 eV), the EL3 trap (Ec−0.63 eV), and the EL6 trap (Ec−0.35 eV), decrease by one order of magnitude. On the other hand, three new electron traps at Ec −0.42 eV, Ec −0.54 eV, and Ec −0.94 eV are created. After rapid thermal annealing up to 550 °C for 10 s, these created traps are reduced and the deep levels decreased by hydrogenation recover nearly completely. This result reveals that the passivation and creation of deep levels by hydrogenation may be explained as the interaction of atomic hydrogen with an unsaturated bond of native defects.