This paper looks into mentoring as a basis for capacity development and service delivery in libraries of higher education in rivers state. The paper highlights the relationship between mentoring and service delivery of library staff in higher institutions in Rivers State Correlational design was adopted for the work. The population of three hundred and sixty two (362) was used comprising of library staff in higher institutions in Rivers States. The entire three hundred and sixty two hundred and twenty (362) population was as sample because the number is manageable. A rating scale designed by the researcher was used for data collection. The instrument was validated by five (5) experts and its reliability was established through a test re-test method using Crombach Alpha Coefficient which yielded an index of 0.816. Descriptive Statistics and Pearson Product Moment Coefficient were used to answer research questions while Pearson Product Moment Coefficient also used for the testing of the hypothesis at 0.05 level of significance. Findings from the study showed that there is a significant relationship between mentoring and service delivery in the libraries of higher institutions in Rivers Based on the findings, the study recommends that mentoring should be made available to the library staff in order to ensure high performance and service delivery.