The foundation of controlling hypertension is adherence to antihypertensive medication adherence. This systematic review and meta-analysis aimed to assess the magnitude and associated factors of adherence to antihypertensive medication among adult hypertensive patients in Ethiopia. A comprehensible bibliographic searching was conducted from PubMed, EMBASE, Scopus, and Web of Science core collection. All published and unpublished studies that had been accessible before 31 May 2020, and written in English were eligible. Joanna Briggs Institute assessment tool was used to evaluate the quality of the findings of the included studies. Stata software 16.0 was used to analyze the data. Study-specific estimates were pooled to determine the overall prevalence estimate across studies using a random-effects meta-analysis model. Publication bias and heterogeneity were checked. Fourteen studies with a total of 4938 hypertensive patients were included in the final systematic review and meta-analysis. The pooled prevalence of medication adherence among hypertensive patients in Ethiopia was 65.41% (95% confidence interval: 58.91-71.91). Sub-group analysis shown that the pooled prevalence of medication adherence was the highest (69.07%, 95% confidence interval: 57.83-80.31, I 2 = 93.51) among studies using questionnaire technique whereas the lowest in Morisky Medication Adherence Scale eight-items (60.66%, 95% confidence interval: 48.92-72.40, I 2 = 97.16). Moreover, medication adherence was associated with the presence of comorbidities (pooled odds ratio = 0.23, 95% confidence interval: 0.07-0.38, p = 0.030, I 2 = 54.9%) and knowledge about the disease and its management (pooled odds ratio = 2.98, 95% confidence interval: 1.72-4.24, p = 0.04, I 2 = 55.55%) but not with place of residence (pooled odds ratio = 1.22, 95% confidence interval: 0.51-1.93, p = 0.00, I 2 = 76.9%). Despite a lack of uniformity among included studies, adherence to antihypertensive medication among the hypertensive population in Ethiopia was moderate. The presence of comorbidities and/or complications reduced the odds of adherence whereas having good knowledge about the disease increased chance of medication adherence among hypertensive patients.