Amid growing global interest in state interventions, this paper examines the impact of Chinese government infrastructure investments on improving firm productivity. It centers on a policy aimed at directing regional governments to foster a more conducive market environment for private enterprises. Our analysis reveals that the positive effect of infrastructure investment on firm productivity is increased by 42.5% for private firms in industries that benefitted from improved market entry opportunities and an even more striking 97.9% in provinces where arbitrary fines were curtailed. These findings underscore the complementary roles of state interventions and the development of market mechanisms in boosting firm productivity.