Abstract This study introduces a novel perspective by examining the influence of clan culture on carbon emission intensity (CEI) in Chinese cities. Clan culture, as a traditional social organization, shapes the informal institutions within modern Chinese society. Empirical findings reveal that the strength of clan culture is significantly negatively correlated with local carbon emission intensity, with a one standard deviation increase in clan culture strength corresponding to a 10.21% reduction in CEI. Additionally, we find that clan culture amplifies the effectiveness of environmental regulations, especially after the 2017 green finance reforms and innovation, fostering environmentally conscious behaviors in communities. Our investigation further highlights that clan culture limits carbon‐intensive industries, enhances government environmental awareness, improves policy implementation, and promotes green innovation. All these findings highlight the critical role of cultural factors in addressing environmental challenges and advancing sustainable practices.