The European Union, like many other international organizations and governments, committed itself during the 1990s to the “mainstreaming” of gender issues across all policy areas at all stages in the policy process. Nonetheless, more than a decade after the Union’s initial commitment, this commitment has not led to consistent and effective implementation. The problem, we argue, lies in the failure to “get the incentives right,” mobilizing sufficient interest among crucial actors, beginning within the bureaucracy of the international organizations or governments in question. Organizations like the European Commission are more successful in achieving their objectives when they provide “hard” incentives for bureaucrats to implement reforms. Cross-cutting mandates are less successful when they depend exclusively on “soft” incentives such as persuasion and socialization. This has been the case, we demonstrate, within the Commission, which has relied exclusively on soft incentives in its implementation of gender mainstreaming, with highly variable results after over a decade. By contrast, we demonstrate, the Commission has utilized hard incentives in the adoption of another cross-cutting mandate, on equal opportunities for men and women officials, resulting in rapid, quantifiable progress. The limited impact of gender mainstreaming on EU policy outputs, therefore, reflects not an inherent flaw of the mainstreaming concept, but rather the Commission’s choice to rely almost exclusively on soft incentives in implementation.