OBJECTIVE To examine the association between religiosity and sexual and contraceptive behaviours in France. METHODS Data were drawn from the 2005 Health Barometer survey, a random sample of 7495 women and 5634 men aged 15 to 44. We used logistic regression models to study the associations between religiosity and sexual and contraceptive behaviours, by gender and religious denomination. RESULTS Three quarters of respondents (73%) reported no religious practice, 20% practised occasionally, and 7% regularly. Regular practice was associated with later sexual debut, regardless of religious denomination. Among participants less than 30 years old, religious respondents were less likely to have used a condom at first sexual intercourse (odds ratio [OR] = 0.2 for women, OR = 0.4 for men) or any form of contraception (OR = 0.2 for women). At the time of the survey, sexually experienced adolescents who reported regular religious practice were less likely to use contraception (84.7% vs. 98.1%, p < 0.001). Regular practice was associated with a 50% decrease in the odds of using very effective methods for Catholics, but had no effect among Muslims. CONCLUSIONS This study, conducted in the French secularised context, shows a complex relationship between religiosity and sexual behaviours, which varies by gender, religious affiliation and during the life course.