Background Globally, hypertension is a major public health problem and a strong predictor of cardiovascular disease complications. To reduce and prevent complications from hypertension, it is important to adapt self-care behaviors. This study aimed to assess the self-care practices of adult hypertensive patients at a tertiary teaching hospital in Ethiopia. Methods A health facility-based prospective cross-sectional study was conducted at Jimma Medical Center in Ethiopia between February 2021 and July 2021. Binary and logistic regression was performed to assess the strength of associations between independent and dependent variables. Data entry and analysis were done using Statistical Package for social science (SPSS) software version 22.0. A p-value < 0.05 was considered to declare statistical significance. Results From a total of 422 respondents included to the study, male accounted 55.7% and the mean ± SD age of the respondents was 58.7 ± 9.75 years. About 53.1% of patients had poor self-care practices toward hypertension. Not attending formal education [AOR = 2.15; 95% CI (1.74, 6.39); p ≤ 0.001], uncontrolled blood pressure [AOR = 2.14 95% CI (1.27, 3.61); p = 0.003], chronic disease co-morbidity [AOR = 1.48; 95% CI (0.25, 7.73); p ≤ 0.001], unfavorable attitude toward hypertension[AOR = 3.13; 95% CI (1.95, 7.52); p ≤ 0.001], and poor social support [AOR = 2.75; 95% CI (1.45, 6.43); p ≤ 0.001] were independent predictors of poor self-care practice. Conclusion The level of self-care practices for hypertension in the study area was low. In particular, the level of adherence to the DASH diet, exercise, and weight control was very low. Patient-specific targeted interventions are required to improve self-care practices for hypertension.