Background: Diagnostic imaging of the head is used with increasing frequency, and often includes the paranasal sinuses, where incidental opacifications are found. Evaluating the clinical relevance of such findings is challenging, and for the patient, such incidental findings can give rise to concern if they are over-reported. Studies of incidental findings in the paranasal sinuses have been conducted mostly in patients referred for diagnostic imaging, hence the prevalence in the general population is not known. There is little study in Ethiopia. so this study will contribute to strong evidence in the field. Objective: To assess the magnitude of incidental Paranasal sinus abnormalities and factors associated with the magnitude of incidental paranasal sinus abnormalities on brain MRI done for patients with other CNS problems in NISIR and Nolot diagnostic centers in Bahir Dar. Method; An institutional-based cross-sectional study was conducted and Systematic random sampling technique was used to select study participants. To collect necessary data structured questionnaire was administered. MRI soft copy images were assessed by a Radiologist. Data was entered using EpiData version 4.6 software and exported to SPSS software version 26. The association between the incidental paranasal sinus abnormalities on brain MRI and independent variables was assessed using a simple binary and multivariable logistic regression analysis. In simple binary logistic regression, variables with a p-value, of less than 0.25 were selected for multivariable analysis, and in multiple binary logistic regression analysis variables with a P-Value, of less than 0.05 was considered statistically significant. Finally, the analyzed data were described using tables, and figures accordingly. Result; of two hundred twenty-eight patients, 132(57.9%) had one or more than one incidental paranasal sinus finding seen. the maxillary sinus was the most commonly affected sinus group followed by the ethmoid sinus. frontal sinus was the least to have incidental abnormalities. Significant Mucosal thickening was the most common type of abnormality seen followed by retention cyst/polyp. The prevalence of incidental paranasal sinus abnormalities was significantly associated with Retroviral infection (AOR:3.273, CI 95%:1.154-8.327, P-value of 0.026), diabetes mellitus (AOR:2.895, CI 95%:1.007-8.327, P value 0.049), and Allergy (AOR:2.932, 95% CI:1.019-8.435, P value 0.046). there was no significant relationship seen between age of the patient, gender, smoking history, place residency occupation, brain tumor, hypertension and seizure, meningitis with a P-value of > 0.05. Conclusion; Our findings revealed that the proportion of paranasal sinuses abnormalities in asymptomatic patients was high at 57.9%. A significant correlation was observed between Diabetes Mellitus, Allergy history, and retroviral infection with incidental sinus findings. Our findings significantly contribute to the knowledge of incidental sinus findings in patients. It will help the radiologists determine the relevance of abnormal findings and consider the possibility of the development of unexpected abnormalities. Keywords; Magnetic resonance imaging, paranasal sinus, incidental abnormalities.