Are proponents of Islamic government in the Arab World more likely to support violent extremist groups like ISIS? Previous research indicates that the answer to this question is dependent on individuals’ beliefs about what constitutes proper Islamic government. In this study I theorize that individuals’ beliefs about the compatibility of Islamic government and democracy is a key predictor of support for armed groups like ISIS. Using 2017 survey data from six Arab countries I find that ‘nondemocratic Islamists’ – those who favor the implementation of Shari’a law and clerical rule but believe Islam to be incompatible with democratic principles – are significantly more likely to express support for ISIS. In contrast ‘democratic Islamists’ – those who view Islamic Government to be congruent with democratic rule – are not more likely to endorse ISIS goals or tactics. These findings underscore the conditional and complex nature of the relationship between Islamism and violent extremism.