This study examined reasons for non-use of condoms among an online survey sample of 462 non-condom using men who have sex with men to: (1) identify major domains, themes and categories encompassing reasons for non-use of condoms and (2) examine whether reasons varied by role-in-sex (insertive or receptive) and meeting venue (online or offline). A thematic analysis was completed on participant responses to an open-ended question about reasons for non-condom use. Preference for not using condoms and contextual factors were the top two reasons given for not using condoms, followed by a reasoned judgment based on risk assessment, relationship status and interpersonal communication. No major differences were found between men who reported non-condom use at last receptive and insertive anal intercourse. By contrast when meeting online, men were more likely to report reasons for non-condom use that corresponded to individual preference and mutual agreement not to use condoms. When meeting offline, men were more likely to cite reasons related to context and relationships. In developing HIV-prevention interventions for this population, researchers should address both venues separately, as reasons why men engage in non-use of condoms appear to differ.