This research examined public relations variables and effective service delivery in Nigerian university libraries, 3 objectives, research questions and hypotheses were formulated to guide the study. Descriptive survey design was used for the study while the area of the study is selected Nigerian federal university libraries. The sample size are 198 librarians from various federal universities in Nigeria while census sampling technique was used for the sampling. The instrument for data collection for this study was a researcher developed questionnaire titled: “public relation variables and effective library services delivery Questionnaire” (PRVELSDQ). The instrument was distributed electronically through whatsapp platforms of the various federal university libraries and through librarian’s emails. The instruments that were properly filled and returned were analysed using mean and standard deviation to answer the research questions while depended t-test was used to analyse the hypotheses at .05 level of significance. At the end of the research, it was discovered that there is a significant influence of public relations on effective service delivery by librarians in federal university libraries. Hence, university libraries should ensure that they utilize human relationship, websites and library displays to easily have out effective service delivery, as it is important to ensure that services are properly, efficiently and effectively carried out in university libraries because librarianship is a service-oriented profession.