In 2003, Nigeria adopted the Family Life and HIV Education (FLHE) sexuality education curriculum. Our analysis interrogates variation in sub-national implementation. We conducted 52 interviews with persons knowledgeable about the curriculum in three states-Kano, Lagos, and Niger-and reviewed publications on FLHE. In Kano, the socio-cultural context impeded implementation, but the persistence of innovative local champions resulted in some success. In Lagos, the cosmopolitan context, effective champions, funding by international donors, and a receptive government bureaucracy led to successful implementation. In Niger, despite a relatively conservative socio-cultural context, state bureaucratic bottlenecks overwhelmed proponents' efforts. In summary, the interaction of socio-cultural context, domestic champions, adaptive capacity of state bureaucracies, and international funders explains variable implementation of FLHE. The Nigerian experience highlights the need for sexuality education proponents to anticipate and prepare for local opposition and bureaucratic barriers.