Background There is little research on men’s contraceptive knowledge, attitudes and beliefs, yet the male partner is known to influence contraceptive choices. This study investigates contraceptive experiences, knowledge, attitudes and beliefs of a sample of sexually active, heterosexual men via an online dating site. Methods: An anonymous online survey was sent to men who had logged onto an online dating site within the previous year. Results: We analysed 2438 survey responses. A contraceptive method was used at last intercourse for 82% of men <50 years old versus 69% of men ≥50 (P < 0.0001). Condoms (35%), vasectomy (22%) and the contraceptive pill (21%) were the most commonly used methods. Older men were less likely to use condoms than younger men (P < 0.0001). More than 80% of participants had heard of each method. The greatest perceived harm was with the emergency contraceptive pill, with 32% responding that it was ‘harmful to the health of the user’ and 37% not sure. Belief that contraception decision-making should be shared between partners increased from 57% in a ‘one-night stand’ to 75% in a casual relationship, to 92% in a long-term relationship. Conclusion: Among this sample there is high contraceptive use, especially vasectomy in older men and a desire to share contraceptive decision-making with their partners, especially in long-term relationships. However, low awareness of some methods and misperceptions about hormonal contraceptive method safety, especially the emergency contraceptive pill, highlight the need for education for men.