Survey findings suggest that predominantly Muslim countries are among the most religious in the world and validate commonly held, but overly simplistic, perceptions of Muslims as extremely and uniformly religious. Existing research has demonstrated that survey estimates can give a distorted view of the reality of levels of religious practice; however, it has thus far focused exclusively on traditionally Christian, advanced Western democracies. To address this oversight, the veracity of self-reported religious practice in the Muslim world is tested using Pakistan, the Palestinian territories, and Turkey as cases for study. Comparing estimates of prayer from conventional surveys with those from time diaries, marginal rates of overreporting are estimated for each country by sex. The time-use measure of prayer is then imputed for the conventional survey data set to estimate overreporting at the respondent level and to predict overreporting using a measure of religious identity importance. Findings suggest that overreporting of prayer occurs in each country considered, although more consistently for women than for men. Moreover, religious identity importance is strongly correlated with overreporting of prayer, suggesting that a similar mechanism may promote the measurement error for overreported prayer in the Muslim world and overreported church attendance in the West.