Introduction: Sexual activity of men has been evaluated at the population-level in different regions of the world. However, reliable data are lacking for Eastern Europe. Therefore, the aim of this study was to analyze the frequency of sexual activity and the number of sexual partners in a large representative cohort of Polish men. Methods: We performed a cross-sectional investigation with computer-assisted web interviews. Participants were stratified by age (≥18 years) and place of residence. The most recent population census was used to produce a population-representative sample of respondents. Men’s sexual activity was then correlated with multiple variables. Results: We enrolled 3001 men, representative for age and place of residence, including adequate proportions of respondents from urban and rural areas. Most Polish men were sexually active, predominantly having had sex at least weekly with one partner. Almost 18% of respondents declined sexual intercourse and/or sexual partner in the prior year. The highest sexual activity was observed for men 35-44-years-old (for sex frequency) and 18-24-years-old (for partner number), living in medium-sized cities, employed, and married (for sex frequency) or divorced (for partner number). Erectile dysfunction negatively affected the frequency of sexual activity and lowered the number of sexual partners, although premature ejaculation did not have any effect. Frequency of sexual activity and number of sexual partners correlated well with psychological distress, quality of sex life, and overall life quality. Whereas lifestyle habits including smoking and alcohol intake decreased the likelihood of sexual activity, all analyzed comorbidities did not affect sex life. Conclusions: This study of men’s sexual activity was the first population-representative and nationwide investigation performed in Poland. Most Polish men were sexually active and sexual activity correlated with multiple variables including sociodemographic factors, erectile functioning, mental distress, overall and sex-specific quality of life, and lifestyle habits.