The study sought to examine the influence of leadership styles and staff motivation on job satisfaction in private university libraries in Osun State, Nigeria. The descriptive survey design was adopted for the study. Data were analyzed using descriptive and inferential statistics. Findings revealed that leadership styles and Staff motivation are predictors of job satisfaction of library staff. There was a high level of job satisfaction among library personnel due to the democratic leadership styles that were predominant. Most of the library staff were highly motivated with a higher level of intrinsic motivation than extrinsic motivation. The study concludes that leadership styles and Staff motivation are predictors of job satisfaction of library staff. Therefore, it is recommended that democratic leadership styles be adopted by libraries with more emphasis on extrinsic motivation