ABSTRACT As a pivotal instrument in environmental governance, voluntary environmental regulation effectively drives corporate green innovation. This study leverages China's Green Factory Certification as a quasi‐natural experiment to examine the causal effect of voluntary environmental regulation on corporate green innovation. Using panel data on 2783 A‐share listed manufacturing firms from 2014 to 2021 and a staggered difference‐in‐differences model, we find that green factory certification significantly enhances corporate green innovation by improving both the quality and quantity of green patent outputs. The results remain robust across multiple robustness checks, including instrumental variable estimation and propensity score matching. Mechanism analysis identifies three channels: incentive, competition, and learning effects. Government incentives increase expected returns, motivating firms to invest in green innovation. Competitive pressure from peers and reputational pressure from stakeholders drive firms to strengthen their green performance. Disclosure requirements foster reflection and learning, enabling firms to align their strategies with green innovation goals. Heterogeneity analysis reveals that the effect is stronger in regions with higher government incentives and more developed markets. The effect is also more pronounced among firms with weaker bank relationships and limited political connections. This study provides new empirical evidence on the impact of voluntary environmental regulation on corporate green innovation, offering policy implications for advancing the green transition and sustainable development.