Out‐diffusion of oxygen in Czochralski silicon wafers annealed at 1000 and 1200 °C under a hydrogen ambient is studied with secondary ion mass spectroscopy (SIMS). The oxygen diffusivity, 1.41×102 exp(−3.1 eV/kT) cm2 s−1, obtained from fitting the oxygen SIMS profile is significantly larger than normally expected. This hydrogen enhancement effect is found at temperatures much higher than those reported (<500 °C) in literature, and is attributed to the direct interaction between in‐diffused hydrogen and interstitial oxygen atoms. Estimation of the oxygen diffusivity made from hydrogen solubility and diffusivity data is in reasonable agreement with the experimental result. It is suggested that the intrinsic/internal gettering may benefit from the enhancement effect as well as a very low surface oxygen concentration, which is also observed in this work, due to hydrogen treatment.