Abstract Keywords: Library services, Open Source Library Management Software, Librarians, University Libraries Introduction: This study investigated the services rendered by librarians using Open Source Library Management Software (OSLMS) in university libraries in the North-Central zone of Nigeria. Methodology: A descriptive research design was adopted, gathering data from 301 librarians across federal and state universities in the zone using a total enumeration sampling approach. The instrument used in this study was a questionnaire, and its reliability, assessed using Cronbach's alpha, yielded a satisfactory coefficient of 0.81. Data collected from the survey underwent analysis using descriptive statistics, including frequency counts, percentages, and mean values. Findings: The findings revealed that the prominent OSLMS used in university libraries in North-Central Nigeria include KOHA, Evergreen, and NewGenLib, with KOHA being the most widely known and used. The majority of respondents agreed that the services provided by librarians using OSLMS in university libraries include web-based OPAC, advanced acquisition, a full catalogue system for library stock management, export and import records, ISO 2709, administration control, MARC 21 and UNIMARC for professional cataloguing and classification, Z39.50 protocol for cataloguing, circulation, management of the database of library users, webbased interface, Management Information System (MIS), and serials control. Conclusion/Recommendations: The study suggested increasing publicity and promotion of various OSLMS to provide a wider choice of library automation systems in the region. Additionally, research on integrated library software in Nigeria's federal, state, and private universities should explore the adoption, functionality, and user satisfaction of OSLMS to enhance library service efficiency.