Using a quasi-natural experiment on local open government data, this study applies a multi-period DID model to assess how partner cities’open government data affect firms’cross-regional cooperative innovation and its mechanisms. The findings suggest that partner cities’ open government data significantly promotes firms’cross-regional cooperative innovation. Mechanism analysis indicates that this occurs by reducing search and matching costs, thereby facilitating cross-regional cooperative innovation. Heterogeneity analysis reveals that higher data quality and better platform construction in partner cities lead to greater levels of cross-regional cooperative innovation. Additionally, the positive effect is more pronounced for private firms, non-high-tech firms, and eastern-region firms. Further analyses show that open government data improves both the quantity and quality of cross-regional cooperative innovation, and prompts firms to substitute intra-regional with cross-regional cooperation.