The level of client satisfaction with the services provided by the hospitals is one critical area that must be assessed continuously. There is the paucity of information on the comparison of the level of client satisfaction from regular and private wing services of public hospitals in Ethiopia. Thus, the current study aims to compare the level of clients' satisfaction in the adult outpatient department among private wing and regular clients and related factors at Nekemte Referral Hospital. Comparative crosssectional study was conducted from May 20 to June 30, 2016. Data were collected from 406 participants and analyzed using SPSS version 20. Exploratory factor analysis was employed for statistical analysis. The overall client satisfaction was 58.16 and 68.84% at regular and private wing, respectively. Staff services, accessibility of healthcare services, physical facility, provider behaviour, type of visit, travel time, marital status, and educational status and how respondents visited the hospital were found to be independent predictors of client satisfaction. Besides, there was no statistically significant mean overall levels of client satisfaction difference between regular and private wing outpatient department. Hence, the hospital management should work towards improving staff services, accessibility of health services, physical facility, and provider behaviour.