ObjectivesMale circumcision (MC) reduces HIV infection by approximately 60% among heterosexual men and is recommended by the WHO for HIV prevention in sub-Saharan Africa. In northwest Tanzania, over 60% of Muslims but less than 25% of Christian men are circumcised. We hypothesised that the decision to circumcise may be heavily influenced by religious identity and that specific religious beliefs may offer both obstacles and opportunities to increasing MC uptake, and conducted focus group discussions to explore reasons for low rates of MC among Christian church attenders in the region.DesignQualitative study using focus group discussions and interpretative phenomenological analysis.SettingDiscussions took place at churches in both rural and urban areas of the Mwanza region of northwest Tanzania.ParticipantsWe included 67 adult Christian churchgoers of both genders in a total of 10 single-gender focus groups.ResultsChristians frequently reported perceiving MC as a Muslim practice, as a practice for the sexually promiscuous, or as unnecessary since they are taught to focus on ‘circumcision of the heart’. Only one person had ever heard MC discussed at church, but nearly all Christian parishioners were eager for their churches to address MC and felt that MC could be consistent with their faith.ConclusionsChristian religious beliefs among Tanzanian churchgoers provide both obstacles and opportunities for increasing uptake of MC. Since half of adults in sub-Saharan Africa identify themselves as Christians, addressing these issues is critical for MC efforts in this region.