Abstract Background Hypertension constitutes a growing burden of illness in developing countries like Zambia. Adequately screening and treating hypertension could greatly reduce the complications of stroke and coronary disease. Our objective was to determine the prevalence of hypertension and identify current treatment practices among adult patients presenting for routine care to rural health facilities in the Better Health Outcomes through Mentoring and Assessments (BHOMA) project. Methods We conducted a retrospective analysis of routinely collected clinical data from 46 rural government clinics in Zambia. Our analysis cohort comprised patients ≥ 25 years with recorded blood pressure measurements, who sought care at primary health centers. Consistent with prior research, in our primary analysis, we only included data from first visits. Hypertension was defined as a systolic blood pressure ≥140 mmHg, or diastolic blood pressure ≥90 mmHg, or reported use of antihypertensive medication. A sensitivity analysis was performed using median blood pressure for individuals with multiple visits. Results and Discussion From January 2011 to December 2014, 116,130 first visits by adult patients met eligibility criteria. The crude prevalence of hypertension by onsite measurement or reported use of antihypertensive medication was 23.1 % [95 % CI: 22.8-23.3] (23.6 % in females, 22.3 % in males). The age standardized prevalence of hypertension across participating sites was 28.0 % [95 % CI: 27.7-28.3] (29.7 % in females, 25.8 % in males). Sensitivity analysis revealed a similar prevalence using data from all visits. Only 5.6 % of patients had a diagnosis of hypertension documented in their medical record. Among patients with hypertension, only 18.0 % had any antihypertensive drug prescribed, with nifedipine (8.9 %), furosemide (8.3 %), and propranolol (2.4 %) as the most common. Conclusions Age standardized prevalence of hypertension in rural primary health clinics in Zambia was high compared to other studies in rural Africa; however, we diagnosed hypertension with only one measurement and this may have biased our findings. Future efforts to improve hypertension control should focus on population preventive care and primary healthcare provider education on individual management.