Background: Rheumatic heart disease (RHD) is a major cause of preventable premature cardiovascular-related death in developing countries. However, information regarding adherence rates and associated factors is limited and inconsistent in Ethiopia. Methods: A cross-sectional study was conducted from August to November 2019 among selected RHD patients on follow-up at four hospitals in Jimma zone. Data were collected using a structured questionnaire. Adherence of RHD patients to secondary prophylaxis in the previous consecutive 12 months was assessed based on the annual frequency of received prophylaxis (monthly injection of benzathine penicillin). Good adherence was considered the patient receiving >80% of the annual dose. The collected data were entered into Epidata 3.1 and analysed using SPSS 23. Results: A total of 253 RHD patients taking prophylaxis were included in the analysis, and of those 178 (70.4%) were female, giving a male:female ratio of 1:2.4. The mean age was 24 ±11 (6-65) years. About 63% had good adherence to benzathine penicillin prophylaxis. New York Heart Association functional class I and II, rural residence, >30 km from health facility, and duration of prophylaxis >5 years were associated with poor adherence (respectively: AOR 12.6 [95% CI 2.5-63], P=0.