PurposeThe study examined capacity-building practices for librarians' effective library service delivery in Federal University Libraries in Nigeria.Design/methodology/approachThe design for this paper was a descriptive survey research design. Data was collected using a questionnaire from a total number of 178 respondents. Collected data were analyzed using mean scores and standard deviation.FindingsThe findings reveal that learning capacity-building practices such as rotating members of staff for wider experience exist in these libraries. Learning capacity-building practices contributes to effective service delivery by enhancing various library services. Results also show that there are challenges confronting learning capacity-building practices which include inadequate funding. For these libraries to perform to their highest potentials, their learning capacity needs to be built and developed.Research limitations/implicationsThe major limitation of this study is the tendency of the respondents to fake their responses which may arise from their personal biases.Practical implicationsTherefore, university library management and university administrators should as a matter of urgency develop policies that will ensure that capacities are built for better service delivery or risk users losing interest in the library.Originality/valueThe study examined a vital dimension of capacity build, which is learning capacity building. The findings will help university administrators and library management to know the different learning capacity-building practices that exist in the various libraries and the extent to which these practices are important and relevant for effective service delivery. This will assist them in adopting relevant and adequate learning capacity-building strategies and guiding them in formulating effective capacity-building policies.