While public opinion research has expanded rapidly in the Islamic world since 2001, little scholarly work has examined interviewer effects related to an enumerator's religious adherence. We find that the perceived religiosity of an interviewer impacts respondents' expressions of personal piety and adherence to Islamic cultural norms in a sample of approximately 1,200 women in Greater Cairo. Muslim women indicate that they are more religious and adherent to Islamic cultural norms when interviewed by an enumerator donning the Islamic headscarf. Conversely, members of Egypt's minority Coptic Christian community report that they are less adherent to Christianity when interviewed by a veiled enumerator. Through psychological processes of strategic self-presentation of identity and impression management, the veil may trigger Muslim respondents to express what they perceive to be socially desirable (i.e., more devout) responses; in contemporary Egypt, being perceived as pious may elicit social and economic benefits. Christians appear to deemphasize their religious identity to avoid appearing at odds with the dominant, Muslim majority to which the enumerator appears to belong. Younger, poorer and less educated women — who may be most susceptible to concerns about social desirability — show the largest effects.