Tanzania official statistics on religion are unavailable because religious surveys were eliminated from government census reports after 1967. Religious leaders and sociologists estimated in 2007 that Muslim and Christian communities were approximately equal in size, each accounting for 30 to 40 percent of the population, with the remainder consisting of practitioners of other faiths, indigenous religions, and people of “no religion”.

According to an estimate from 2014, 61.4 percent of the population was Christian, 35.2 percent was Muslim, 1.8 percent practiced traditional African religions, 1.4 percent were unaffiliated with any religion, and 0.2 followed other religions. Nearly the entire population of Zanzibar is Muslim. Of Muslims, 16 percent are Ahmadiyya (although they are often not considered Muslims), 20 percent are non-denominational Muslims, 40 percent are Sunni, 20 percent are Shia, and 4% are Sufi.

The Christian population is mostly composed of Roman Catholics and Protestants. Among Protestants, the large number of Lutherans and Moravians points to the German past of the country, while the number of Anglicans point to the British history of Tanganyika. Pentecostals and Adventists are also present because of missionary activity. All of them have had some influence in varying degrees from the Walokole movement (East African Revival), which has also been fertile ground for the spread of charismatic and Pentecostal groups.

There are also active communities of other religious groups, primarily on the mainland, such as Buddhists, Hindus, and Bahá’ís.