Sexual health influences general well-being and the overall quality of life of all men and women. This study in Shiraz, Islamic Republic of Iran, aimed to assess the level of knowledge of and attitudes towards sexual and reproductive health among adults. In a cross-sectional study in 2010, 276 men and 281 women were recruited at pre-marital counselling courses and completed a 33-item anonymous questionnaire in private. The overall level of knowledge of men and women was low. Both men and women had low scores on knowledge of genital anatomy, sexually transmitted infections and contraceptive use. The majority of participants had positive attitudes towards implementing educational programmes on sexual and reproductive health issues for young adults and prior to marriage. Efficient educational programmes providing up-to-date information about sexual and reproductive health are needed in the Islamic Republic of Iran.