Chronic kidney disease (CKD) and stroke share many common risk factors, and the presence of CKD confers added risk factors for stroke. With increasing interest and understanding of the close relationship between the kidney and the brain, this study aims to assess the prevalence and impact of renal dysfunction on outcomes acute stroke patients. This is a prospective hospital-based study carried out in the neurology unit of University of Maiduguri Teaching Hospital, Maiduguri, northeastern Nigeria. The study population consisted of adult patients (>18 years) admitted in the medical wards with a diagnosis of acute stroke. Sociodemographic variables and biochemical parameters were obtained from each patient. Patients' functional status assessment by modified Rankin scale, Barthel index, and National Institutes of Health Stroke Scale score were obtained at admission and discharge. Glomerular filtration rate (GFR) was calculated using the modification of diet in renal disease equation. Patients who have estimated GFR (eGFR) <60 mL/min/1.73 m2 were considered to have CKD. Patients were grouped into A: with GFR <60 mL/min and B: GFR >60 mL/min. Out of a total of 501 patients admitted during the study period, 448 patients had complete data and were recruited, out of which 275 (61.4%) were male and 173 (38.6%) were female. Their ages ranged from 38 to 89 years, with a mean age ± standard deviation of 53.85 ± 18.13 years. The mean eGFR of the study population was 66.55 ± 30.49 mL/min. Two hundred and twenty-five (50.2%) had renal dysfunction with GFR <60 mL/min. The mean GFR of patients with renal dysfunction was 32.84 ± 27.59 mL/min, and patients without renal dysfunction had a mean GFR of 73.68 ± 35.61 mL/min. Patients with renal dysfunction on admission had Barthel stroke score of 20.74 ± 18.74 as compared to patients without renal dysfunction (25.49 ± 20.34), P = 0.017. At discharge, the Barthel scores for the two groups were 53.87 ± 30.17 and 41.71 ± 30.29 (P = 0.000), respectively. Patients with renal dysfunction had longer hospital stay with a mean duration on admission of 45.66 ± 39.90 days and severe residual disability at discharge. Acute stroke patients who have associated renal dysfunction have severe disability on admission and discharge. Renal dysfunction is common among acute stroke patients.