service quality of professional librarians in public university libraries in South-South Nigeria. The research \r\nadopted a descriptive survey design, targeting 400 librarians across four major public universities. Data \r\nwere collected using a self-structured questionnaire validated for reliability and analysed using weighted \r\nmeans and One-Way Analysis of Variance (ANOVA). The study found that librarians with high self-efficacy \r\ndemonstrated greater confidence in handling complex library tasks, digital resources, and user inquiries, \r\nwhich significantly enhanced service quality. Similarly, strong interpersonal relationship skills, including \r\ncommunication, empathy, and teamwork, positively influenced librarians’ interactions with users and \r\ncolleagues, resulting in improved satisfaction and efficiency. The combined effect of self-efficacy and \r\ninterpersonal skills was found to be a stronger predictor of service quality than either factor independently. \r\nThe study highlights the need for continuous professional development programmes that enhance both \r\ntechnical competence and relational skills among librarians. It also underscores the importance of \r\nmentorship, peer learning, and structured feedback systems in fostering high-performing library staff. \r\nFindings provide empirical evidence for library administrators and policymakers to prioritise competency \r\ndevelopment as a strategic approach to improving library service delivery. The study fills a significant \r\nresearch gap in understanding how individual competencies influence library service quality in the \r\nNigerian higher education context and offers practical recommendations for human resource interventions \r\naimed at sustaining high standards of library services.