The health care industry is undergoing a rapid transformation to meet the ever-increasing needs and demands of its patient population. Level of patients' satisfaction is an important health outcome, which is regarded as a determinant measure for quality of care. This study was performed with the aim of assessing the level of patient satisfaction with inpatient services and its determinants in Black Lion Specialized Hospital, Addis Ababa, Ethiopia. A facility-based cross-sectional study was conducted from November 25th to December 20th, 2015, using 398 randomly selected patients. Ethical clearance was obtained from the Jimma University research review board, and verbal consent was also received from the study participants during data collection time. A pretested structured interview questionnaire was used to collect data from study participants. The collected data were handled by using SPSS statistical software. Before analysis, relevant explanatory variables were identified using factor analysis with varimax rotation, and bivariate analysis was carried out using linear regression for every independent variable with the outcome variable independently. Explanatory variables scoring p value <-0.05 were used for the final model after checking the assumption. Study findings are presented by using tables, graphs, and description. A total of 398 patients were participated in the study, yielding a response rate of 100%. A total of 46.2% (95% CI: 41.2%-51.1%) patients were satisfied by the services they received in the hospital. Patient and health care provider interaction and general facility amenity-related domains were found to explain 96.4% of the variability in the net overall satisfaction score. Good quality services provided by hospital physicians, availability of laboratory and radiology services, pain management services, and inpatient pharmacy services of the hospital had positive influences. Besides toilet cleanliness, availability of rooms for accommodation and dietary service had significant relation with level of patient satisfaction. Quality of the inpatient pharmacy service had a great influence on satisfaction; a unit increase in it resulted in 2.3 (95% CI: 2.1-2.5) times increment in patient satisfaction level at p ≤ 0.001. For final predictors, regression estimates for level of satisfaction moved from very dissatisfied to very satisfied when service improves by a unit. Overall patients' satisfaction is lower than other studies in the nation. A great opportunity is there to improve patient's satisfaction level if the service quality is improved around the time of patient and health care provider interaction and facility amenity services. Besides, improving the health literacy of service providers and devising a strategy to routinely assess satisfaction level of patients in the facility is critical. On top of this, providing tailored on-the-job training for health care workers in the facility is a crucial step in order to improve their knowledge and skills to render patient-centered quality service to improve their patients' satisfaction. Using a checklist during service delivery may improve client patient interaction and ensure the standard. Facility design dimension can be considered for future research activities.