Background - Hearing impairment affects millions of people around the world and currently it is estimated to be the fourth leading cause of disability globally. Although the problem is greater in sub-Saharan Africa including Ethiopia, it is a hidden problem that still receives little attention from researchers, policymakers and other stakeholders. Objective - The aim of this study was to assess hearing impairment and associated factors among adult patients in ear, nose and throat clinic of Saint Paul’s Hospital Millennium Medical College, Addis Ababa, Ethiopia, 2018/2019. Methods - Institution based cross-sectional study was conducted on 233 study participants from November 20, 2018 to January 20, 2019 at ear, nose and throat clinic of Saint Paul’s Hospital Millennium Medical College. The study participants were selected through convenience sampling technique. Otoscopic examinations and audiometry examinations were performed. Additional data were collected by using a pre-tested structured interviewer-administered questionnaire. Data were entered into EpiData version 4.2 software and then exported to STATA version 14.0 for analysis. Binary logistic regression model was used to assess the association of an independent variable with the dependent variable. Statistical significance was interpreted using the adjusted odds ratio with a 95% confidence interval and a p-value <0.05. Results were presented using text, tables and figures. Result - Out of the total two hundred thirty-three participants, 144(61.80%) had conductive hearing loss. Age from 18-49 years [AOR: 11.86(95% CI: 5.80, 24.27)] and otitis media [AOR: 2.36 (95% CI: 1.24, 4.49)] were significantly associated factors for conductive hearing loss. On the other hand, 104 (44.63%) participants had sensorineural hearing loss. Age from 50-80 years [AOR: 9.48(95%CI: 4.73,18.99)], hypertension [AOR: 2.43 (95% CI: 1.08, 5.45)] and meningitis [AOR: 3.56 (95%CI: 1.08, 11.69)] were significantly associated factors for sensorineural hearing loss. In addition, 64(27.46%) participants had MHL. Age from 50-80 years [AOR: 3.34 (95% CI: 1.66, 6.72)] and higher level of education [AOR: 0.18 (95% CI: 0.05, 0.65)]) were significantly associated factors for mixed hearing loss. Conclusion and recommendations - More than half of the study participants had conductive hearing loss. Age, otitis media, meningitis, hypertension and higher level of education were the identified factors of hearing loss in this study. Therefore, all concerned bodies should work together and focus on the identified factors for early prevention of hearing loss.