The European Commission has played a crucial role in promoting ambitious EU climate targets and policies that boost the credibility of EU leadership-by-example efforts internationally. The approach has gradually shifted from leadership toward more strategic behavior that reflects the preferences of the member states. Reduced uncertainty concerning member-state preferences and solutions accounts for much of the change in leadership. Uncertainty has decreased as climate policies have become more mature and member states have gained experience from implementing them. Asymmetries in member-state preferences, decision-making procedures, and impatience caused by the international context are all important conditions for the European Commission’s leadership. These observations lend support to apparently contradictory theories that have seen EU climate policy as propelled either by autonomous supranational institutions or by increasingly ambitious member states.