Marketing of library resources and services has become a vital approach for promoting awareness, engagement, and effective utilization among undergraduate students in Nigerian universities. This study examined the marketing practices adopted by Ogun State University Libraries and their influence on students’ utilization of resources and services. A descriptive survey design was employed, and data were collected from 210 professional and paraprofessional library staff using a validated instrument titled Marketing of Library Resources and Services Questionnaire (MLRSQ). Descriptive statistics including mean and standard deviation were used for data analysis. Findings revealed that electronic databases, institutional repositories, and current awareness services were the most actively marketed, while reprographic and user education services received less attention. Social media platforms, library websites, and lecturer collaborations emerged as the most frequently used marketing strategies, though implementation was at a moderate level. The major challenges identified included inadequate internet connectivity, insufficient funding, and limited professional marketing skills. The study concludes that while marketing efforts in Ogun State University Libraries have improved visibility, underutilization persists due to weak infrastructural and institutional support. The study recommends strengthening digital marketing infrastructure, formulating clear marketing policies, enhancing funding among others to foster sustainable utilization of library resources and services among undergraduate students. Keywords: Marketing, Library Resources, Library Services, Utilization, Undergraduate Students, University Libraries