Dissertation ( MA Demography)The study finds out how Islamic teaching influences family size in Zanzibar in Central District. It assumes that, the couples‟ preference toward Islamic religious beliefs influence the number of the children couples could have, hence affecting the family size. Literatures show that, studies on religious beliefs on child bearing behaviours concentrated on South Asian and Middle East countries due to strong impact of Islamic teachings in those areas but, little was known on the influence of Islamic teaching on family size in Tanzania. Therefore, a survey was conducted in Central District in Zanzibar to investigate this issue. The study was conducted at three wards in Central District. A total of 120 households were surveyed. Purposive and simple random sampling was adopted to select households to be included in the study. Data analysis test was performed to test for the association Islamic teaching and family size. Quantitative analysis from data progression ratio and childbearing stopping behaviour shows that couples preference for family size is upward in Central District. The findings show that couples continue having children according to religious beliefs. Also the study found that existing Islamic teaching in Central District which was associated with religious beliefs as well as socio-cultural beliefs determined fertility. The study concluded that an Islamic religious belief was a factor toward large family size in Zanzibar. Owing to the influence of education in reducing the rate of childbearing, the study recommends the effort should be taken by government to reduce and control child bearing among muslims community by promoting education to both male and female prospective partners in the society.