This study investigates the influence of Library 4.0 adoption on organisational climate of library professionals in public universities in Lagos State, Nigeria. A quantitative research approach was adopted using total enumeration sampling of 191 library professionals across four public universities: University of Lagos (UNILAG), Lagos State University (LASU), Lagos State University of Education (LASUED), and Lagos State University of Science and Technology (LASUSTECH). Data were collected through a structured questionnaire and 156 valid responses were analyzed using descriptive and inferential statistics, including regression analysis. Findings revealed a moderate to high level of Library 4.0 use among library professionals (aggregate mean = 2.98), with perceived usefulness scoring highest (mean = 3.16) and actual usage lowest (mean = 2.89). Organisational climate was highly positive (aggregate mean = 3.19), with strong person-job fit (mean = 3.43) and person-organisation fit (mean = 3.18), but weaker person-group fit (mean = 2.96). Regression analysis demonstrated that Library 4.0 use significantly and positively influences organisational climate (R = 0.551, R² = 0.304, β = 0.551, p < 0.001), accounting for 30.4% of the variance in organisational climate. The study concludes that increased adoption of Library 4.0 technology contributes significantly to a positive organisational climate among library professionals. However, while technological adoption and role alignment appeared strong, attention should be directed toward improving interpersonal and collaborative group dynamics within the university libraries.