Bronchial asthma is a major public health issue that affects patients, families, and communities worldwide. Despite the growing importance of self-management and its clear link to better health outcomes, the uptake and use of self-management among asthmatic patients is not well understood. Thus, the study aimed to determine the level of self-management practice and associated factors among asthmatic patients on follow-up care at public tertiary hospitals found in south-west Ethiopia. An institutional-based cross-sectional study design was employed from August 1 to September 30, 2022. The study included all asthmatic patients on follow-up care at public tertiary hospitals found in south west Ethiopia, among whom 274 were interviewed. All asthmatic patients who were registered at the chronic follow-up unit of each hospital and fulfilled inclusion criteria were included and interviewed consecutively. The data were collected using a structured interviewer-administered questionnaire adapted from previous studies, entered into EpiData version 4.6, and exported to SPSS version 25 for analysis. Descriptive statistics were used to summarize the participant's characteristics. Linear regression was used to identify variables associated with asthma self-management practice, and variables with a p-value of 0.05 were considered statistically significant. Finally, tables, graphs, and text were used to present the data. Out of 274 interviewed asthmatic patients, 45.26% 95% CI (39, 51) had good asthma self-management practices. Advancing in age (ß = -0.009, P = 0.043), being a smoker (ß = -0.346, 95%, P = 0.03, being alcohol drinker (ß = -0.217, P = 0.001), having depression (ß = -0.038, P = 0.005), having anxiety (ß = -0.029, P = 0.02) and having social support (ß = 0.022, P<0.001) were identified as factors affecting asthma self-management practice. The finding revealed that four of every nine asthmatic patients had good asthma self-management practices. Age, alcohol consumption, smoking, anxiety, depression, and social support were significantly associated with asthma self-management practice. Ongoing self-management support and collaborative target interventions aimed at improving asthma self-management practices and identified factors are very crucial.