As an important breakthrough in coordinating economic, social, and ecological benefits, green innovation has received wide attention from governments, firms, and the public. However, existing studies mainly explored the economic factors influencing firms' green innovation while neglecting social factors. This study took common institutional ownership as the research perspective to explore whether firms' green innovation decisions are affected by their peers. Using a sample of Chinese A-share listed firms from 2003 to 2019, this paper found that firms imitate their peers' green innovation in common institutional ownership networks and exhibit green innovation peer effects. Mechanism testing revealed that "voting with hands" through common institutional ownership helps firms obtain green innovation information (informationbased imitation), while "voting with feet" through common institutional ownership helps firms maintain a competitive awareness of green innovation (rivalry-based imitation), thereby contributing to green innovation peer effects in common institutional ownership networks. Heterogeneity analysis showed that firms with greater financing constraints and lower levels of risk-taking are more likely to imitate their peers' green innovation. Moreover, firms only regard peers with similar industry status and identical property rights as imitation targets in common institutional ownership networks, thereby following "the imitation law of closer preference." An analysis of economic consequences revealed that green innovation peer effects in common institutional ownership networks are not strategic behaviors of "quantity over quality," with imitation contributing to improving firm value. This paper enriches existing research on the influencing factors of green innovation and provides a new reference for promoting sustainable development.