Drawing on approach–inhibition theory and proactivity research, this study examines the potential dark side of peer proactive personality for employee innovative behavior by exploring the mechanism through which peer proactive personality hinders employee innovative behavior and the underlying boundary condition. To test the hypotheses, we conducted a three-wave field study using a nested dataset (i.e., 861 employees and their 122 leaders) in China and an experimental vignette study with a U.S. sample. The results supported our hypotheses that peer proactive personality has a negative effect on employee innovative behavior via reduced employee sense of power, depending on the level of team cooperative climate. This study shifts research attention from the focal employees' proactive personality to peer proactive personality and advances the proactive personality literature by highlighting the potential dark side of peer proactive personality.