BACKGROUND: There are no current pharmacological therapies to improve sperm quality in men with sub-fertility. Reducing the exposure to lifestyle risk factor (LSF) is currently the only intervention for improving sperm quality in men with sub-fertility. No previous study has investigated what proportion of men with sub-fertility are exposed to adverse lifestyle factors. Furthermore, it is not known to what extent men with sub-fertility are aware of lifestyle factors potentially adversely impacting their fertility. METHODS: A cross-sectional anonymous questionnaire-based study on self-reported exposure and awareness of LSF was conducted in 1149 male partners of couples investigated for sub-fertility in a tertiary andrology centre in London, UK. RESULTS: Seventy-percent of men investigated for sub-fertility had ≥1 LSF, and twenty-nine-percent had ≥2 LSF. Excessive alcohol consumption was the most common LSF (40% respondents). Seventeen-percent of respondents used recreational drugs (RD) regularly, but only 32% of RD users believed RD impair male fertility. Twenty-five-percent of respondents were smokers, which is higher than the UK average (20%). Twenty-seven percent of respondents had a waist circumference (WC) >36inches (91cm), and 4% had WC >40inches (102cm). Seventy-nine-percent of respondents wanted further lifestyle education to improve their fertility. CONCLUSIONS: Our data suggest that men with sub-fertility are: (1) exposed to one or more LSF; (2) have incomplete education about how LSF may cause male sub-fertility; (3) want more education about reducing LSF. Further studies are needed to investigate the potential of enhanced education of men about LSF to treat couples with sub-fertility.