Introduction Epilepsy is a widespread neurological disorder characterized by recurrent unprovoked seizures; it contributes to 1% of the global burden of diseases and can end in cognitive impairment. Objective To assess the magnitude and associated factors of cognitive impairment among patients with epilepsy. Method The study utilized an institution-based cross-sectional study design. All patients with epilepsy whose ages were above 18 years were the source population. The authors performed bivariate and multivariate logistic regression analyses. Finally, variables with a p-value <.05 were significantly associated. Result The magnitude of cognitive impairment is 25.6%. Having no family history of epilepsy (AOR=0.12; 95% CI [0.02, 0.61]), polytherapy (AOR=5.14; 95% CI [1.12, 23.62]), and medication-related complaints (AOR=8.24; 95% CI [1.87, 36.38]) were strongly associated with cognitive impairment. Conclusion Significant numbers of patients were positive for cognitive impairment. Family history, polytherapy, and medication-related complaints were associated factors.