Segregation at metal alloy surfaces has an important impact on their catalytic and chemical properties. We have performed density‐functional theory calculations to investigate the surface segregation behaviors of Ni3M (M = Mo, Co, Fe) alloys in the presence of chemisorbed atomic oxygen. The calculated results show that the segregation trend at a Ni3M(111) surface can be substantially modified by reactive gaseous environments. At an oxygen coverage of 1/4 ML, both the Ni‐segregated and M‐segregated surfaces are still less stable than the nonsegregated one for Ni3Fe alloy, while an M‐segregated surface is more stable than the nonsegregated one for Ni3M (M = Mo, Co) alloys. Furthermore, the analysis of oxygen adsorption trends and surface electronic structures explains that the surface segregation trend is directly correlated to the surface–adsorbate binding strength. The present study provides valuable insight for exploring practical applications of Ni‐based alloys as hydrogen‐evolution electrodes.