BACKGROUND: There are limited data on large-scale, multilevel implementation research studies to improve hypertension diagnosis, treatment, and control rates at the primary healthcare (PHC) level in Africa. We describe the characteristics, treatment, and control rates of patients with hypertension in public PHC centers in the Hypertension Treatment in Nigeria Program. METHODS: Data were collected from adults at least 18 years at 60 public PHC centers between January 2020 and November 2020. Hypertension treatment rates were calculated at registration and upon completion of the initial visit. Hypertension control rates were calculated based on SBP and DBPs less than 140/90 mmHg. Regression models were created to evaluate factors associated with hypertension treatment and control status. RESULTS: Four thousand, nine hundred and twenty-seven individuals [66.7% women, mean (SD) age = 48.2 (12.9) years] were included. Mean (SD) SBP was higher in men compared with women [152.9 (20.0) mmHg versus 150.8 (21) mmHg, P = 0.001]. Most (58.3%) patients were on treatment at the time of registration, and by the end of the baseline visit, 89.2% of patients were on treatment. The baseline hypertension control rate was 13.1%, and control was more common among patients who were older [adjusted OR (95% CI) 1.01 [1.01 -1.02)], women [adjusted OR (95% CI) 1.30 (1.05- 1.62)], who used fixed dose combination therapy [adjusted OR (95% CI) 1.83 (1.49 -2.26)], and had higher education levels. CONCLUSION: This baseline report of the largest facility-based hypertension study in Africa demonstrates high hypertension treatment rates but low control rates.