The rise of unintended pregnancies and transmission of STIs and HIV/AIDS among young people is a growing public health problem in Brazil. To design effective interventions, it is necessary to understand the sources that affect their sexuality. Research in developed countries suggests that parents are an important influence. Whether this is also the case in Brazil however, remains unknown as previous studies have largely ignored this question. This study aimed to explore parental influence on the sexual knowledge, attitudes, timing of first sex and contraceptive behaviour of young men and women in a low- income community of Brazil. Parental influence was investigated by focusing on eight factors: verbal sexual communication; parental sexual attitudes; quality of relationship with parents; parental control and other measures of non-verbal communication that have seldom been researched. 1077 young people aged 13-24 from two secondary schools completed a survey questionnaire and 8 focus groups and 138 in-depth interviews were held with young people and parents. Of the 8 parental factors investigated, 5 were related to one or more of the sexuality outcomes: Verbal sexual communication was related to all four outcomes; parental sexual attitudes to young people's own attitudes and the timing of first sex of males; quality of relationship with parents to the attitudes of females and timing of first sex of males; parental control to the sexual knowledge and condom use of young men and the timing of first sex of young women; father's non-verbal feelings towards sex-related scenes on TV was related to the attitudes of both genders and condom use of males. Similar patterns of influence also emerged from the in-depth interviews as did information about how the influences may operate. The results indicate that in the context studied, parents influence young people's sexuality and should be included in future interventions.