Alcohol consumption is frequent among university students in Lebanon as elsewhere in the world. A cross-sectional study was conducted in Lebanon’s public and private universities between October 2009 and September 2010 using a standardized questionnaire to assess personal beliefs about alcohol consumption, peers’ behaviours and opinions and history of and current drinking practices. Of 1235 students, 199 (16.1%) had an AUDIT score ≥ 8. Older age, male sex, Christian religion, attending a private university, studying a non-health specialty and residing in Beirut or Mount Lebanon were associated with a higher risk of harmful drinking. Beliefs concerning alcohol consumption and peers’ opinions and behaviours were factors significantly associated with harmful drinking, especially ignoring the dangers of alcohol consumption; higher frequency of consumption with friends; and a higher proportion of friends who drank regularly. University students’ alcohol drinking behaviour was mostly influenced by peers’ behaviour, and a peer education programme is recommended to decrease the risk of harmful drinking.