This study examines the relationship between family firms and carbon emissions using a large cross-country dataset of 6600 non-financial firms over the period 2010–2019. We find that family firms emit less carbon than non-family firms, especially after the Paris Agreement. Several factors contribute to this outcome, including governance structure, the degree of family control, R&D spending, and the issuance of green patents. Our study also shows that despite lower carbon emissions, family firms have lower environmental scores, primarily due to their reduced public commitment to emission reduction. Both environmental scores and carbon emissions increase when non-family CEOs are appointed and when family ownership decreases, indicating that agency conflicts may influence these outcomes.