Avian influenza (AI) viruses cause disease in domestic and wild bird species. Although these viruses have been reported to occur in poultry in Uganda, risk factors for their introduction and spread were largely unknown. We investigated the seroprevalence and risk factors for exposure of free-range poultry to AI viruses in Important Bird Areas (IBAs) in the country. A structured questionnaire was administered to 664 respondents, and 1342 sera were collected from poultry. Sera were analyzed for antibody titers against AI using competitive ELISA. AI antibody prevalence was 7.6% (95% confidence interval [CI]: 6.2-9.0) in the Lake Victoria Basin, 8.4% (95% CI: 7.0-9.8) in the southwestern region, and none (0/432) in the Kyoga region. High proportions of risky practices were observed among respondent farmers. Significant predictors for exposure of poultry to AI viruses were the source of restocking poultry, method of disposal of inedible parts of slaughtered poultry, and waterfowl visits to a nearby body of water. In addition, visits by waterbirds to a nearby body of water during October-December were more associated with exposure to AI viruses (odds ratio = 3.6; 95% CI: 1.42-9.23) compared with January-March visits'. These results suggested the existence of several risk factors for exposure of free-range to AI viruses in IBAs in Uganda.