This study explored pupils' perceptions of sex and reproductive health education in primary schools in Tanzania. Specifically, the study aimed at (i) exploring pupils' views on sex and reproductive health education in primary schools; (ii) determining opinions on the appropriateness of sex and reproductive health education for pupils in primary schools; and (iii) exploring pupils' views on the influence of culture on sex and reproductive health education to pupils in primary schools. The study was conducted in primary schools in Kinondoni Municipality. Purposive and stratified simple random sampling techniques were employed to obtain 132 respondents amongst science teachers and pupils in standard five, six and seven. Qualitative research approach informed by phenomenological research design was employed to achieve the objectives of this study. Data were collected through interviews and focused group discussion.The findings revealed that majority of teachers and pupils perceive sex and reproductive health education as important for learning in primary schools. Teachers believed that the teaching of sex and reproductive health education is important for a good health of the pupils. Furthermore, findings revealed that education about sex and reproductive health is appropriate to pupils of 10 to 14 years of age. To them, sex and reproductive health education helps to control behaviours and reduce shocks because of the transition period from childhood to adolescence. In addition, it was found that culture did not prohibit pupils from learning sex and reproductive health education. It was concluded that despite teachers and pupils being aware of the existence of sex and reproductive health education, some pupils are affected by cultural and religion backgrounds. The study recommends that schools should educate pupils of the importance of education about sex and reproductive health in primary schools.