Islamist groups that participate in political processes can “succeed” in several different ways, including securing access to resources, initiating and making policy, having their policy preferences co-opted by governing parties, or by discrediting the existing regime. In the contemporary Arab world (including the countries of Egypt, Jordan, Morocco, and Yemen), Islamist parties face formidable obstacles to participating in government and making policy on their own. They are also increasingly starved of resources and repressed by the state, making their one realistic hope for success the de-legitimation of the current regime. By contrast, Islamist parties in Asia (including in Malaysia, Indonesia, and Bangladesh) have more opportunities to compete for influence within the government, with the concomitant potential to influence government policy. Nevertheless, Islamist parties in these Asian countries remain small, with little prospect of controlling elected assemblies. Asian Islamist groups have had profound effects on their political systems, however, through the co-optation of many of their policy preferences by more mainstream nationalist parties. In the process of political competition, Asian Islamists have succeeded in further Islamizing government policies without controlling these policy outcomes directly. They have been able to do this not by focusing on the regime’s legitimacy, but by focusing most directly on social policy, which is open both to negotiation with more powerful actors and to co-optation. Ironically, the Arab Islamists’ move away from social policy towards fundamental issues of democracy and human rights has weakened the government’s interest in engaging the Islamists’ social program and led to increased repression. This has had the effect of mitigating the ability of Islamist groups to substantively influence policy outcomes. Evidence is provided from six cases of policy outcomes in the Middle East and in Asia.