Background: There is paucity of data on the burden of morbidities, clinical characteristics and mortality related to systemic hypertension in Nigeria. The present study therefore aimed to systematically assess the co-morbidities and in-hospital outcomes among hypertensives admitted to 3 Teaching Hospitals in Nigeria. Methods Medical records of all subjects admitted to the medical wards of the study centres with an established diagnosis of hypertension in 2013 were reviewed. Admission, discharge and mortality registers of the medical wards were used to identify the cases, those discharged and those who died. The records of the patients were then reviewed and included if the inclusion criteria were satisfied. Results 288 hypertensive patients were consecutively admitted in the medical wards of the 3 centres in 2013, of whom 146 (59.8%) were males. 88.4% of males and 87.8% of females had 1 or more co-morbidities at admission, and the commonest among all patients was heart failure (HF) followed by stroke/transient ischemic attack (TIA), in 76 (31.2%) and 69 (28.3%) patients respectively. The most frequent co-morbidity among males was HF in 34.3% of them, while stroke/TIA was more common among female patients, in 34.7% of them. Non-cardiovascular co-morbidities were uncommon, and the most frequent was community acquired pneumonia in 7.4% of all patients. 7.8% of all patients (13 males and 6 females; p=0.427) died in-hospital. The deceased had higher systolic blood pressure than the survivors, and majority of them (52.6%) were not on any antihypertensive medications at admission, which was the only predictor of mortality in the present study, increasing its odds by 7.5 fold (odds ratio=7.5; 95%confidence interval=2.8-20.0; p<0.001). Conclusions Co-morbidities were found in more than four-fifths of male and female patients, and the most frequent among males was HF while stroke and TIA were most common among female patients. Non-cardiovascular co-morbidities were uncommon. The prevalence of in-hospital mortality was relatively low, and not being on antihypertensive treatment at admission increased its odds by 7.5 fold.