As environmental sustainability gains prominence, institutional investors are increasingly recognized for their influence on corporate environmental practices. This study investigates how institutional investors’ ownership and investment horizon affect corporate waste management in France. The results reveal that long-term (short-term) institutional investors negatively (positively) affect waste generation. We also show that the effect of long-term institutional investors on waste generation has accentuated after the adoption of the French Law on the Energy Transition in 2015 , especially for firms with high environmental performance and strong corporate governance and those operating in environmentally sensitive industries. These results offer actionable insights for policymakers, investors, and managers seeking to promote sustainable waste management practices.