This research investigated the various staff development practices that lead to capacity building of library staff in private university libraries in Oyo state, Nigeria (Ajayi Crowther University, Lead City University, Precious Cornerstone University, Atiba University, Kola Daisi University and Dominion University). The survey research method was used for the study and the instrument used was the questionnaire comprising of questions drawn up in line with the research objectives. The population of the study comprised of all library staff in the six (6) selected private university libraries (62 in number). Data collected was analysed using percentage and SPSS. The findings of the study revealed that conferences, seminars and workshops were the staff development programmes available in the libraries studied. It was also found that staff request for training formed the major criteria for selecting staff for training with a mean of 3.15, closely followed by the duties assigned to staff with a mean of 3.11. The major challenge facing staff development in the libraries studied was lack of funds with a mean of 3.45 and a lack of clear organisational policy on staff training and development at 3.29. These challenges could be solved through the provision of adequate budgetary allocation for staff training and development. It is recommended that universities should have clear cut policies on staff training and development. Management should have annual budgetary allocation for staff training and development. The Tertiary Education Fund (TETFUND) should also be extended to private universities as corporate bodies and staff of private universities since they also contribute to the economic and manpower development of the country.