introduction Decreasing international financial resources for HIV and increasing numbers of antiretroviral treatment (ART)-treated patients may jeopardise treatment continuity in low-income settings. Using data from the EVOLCam ANRS-12288 survey, this study aimed to document the prevalence of unplanned treatment interruption for more than 2 consecutive days (TI>2d) and investigate the associated individual and health care supply-related factors within the Cameroonian ART programme. methods A cross-sectional mixed methods survey was carried out between April and December 2014 in 19 HIV services of the Centre and Littoral regions. A multilevel logistic model was estimated on 1885 ART-treated patients in these services to investigate factors of TI>2d in the past 4 weeks. results Among the study population, 403 (21%) patients reported TI>2d. Patients followed up in hospitals reporting ART stock-outs were more likely to report TI>2d while those followed up in the Littoral region, in medium-or small-sized hospitals and in HIV services proposing financial support were at lower risk of TI>2d. The following individual factors were also associated with a lower risk of TI>2d: living in a couple, having children, satisfaction with attention provided by doctor, tuberculosis co-infection and not having consulted a traditional healer. conclusions Besides identifying individual factors of TI>2d, our study highlighted the role of health care supply-related factors in shaping TI in Cameroon's ART programme, especially the deleterious effect of ART stock-outs. Our results also suggest that the high proportion of patients reporting TI could jeopardise progress in the fight against HIV in the country, unless effective measures are quickly implemented like ensuring the continuity of ART supply. keywords HIV, Cameroon, antiretroviral treatment interruption, individual factors, health care supply-related factors