This study explored supervisor’s support and career mentoring as a determinantsof public sector succession planning in Nigeria. Specifically, the study investigated the effect of supervisor’s support and career mentoring on succession planning in the Nigeran Public Sector. A descriptive survey research design was adopted for the study. The population of the study comprised the public university staff in Ekiti State. The sample size was 370. Primary data used for the study were gathered through the administration of structured questionnaire. Data gathered were analyzed using multiple regression. The study found that supervisor’s support has significant effect on succession planning. Furthermore, the study found that career mentoring has significant effect on succession planning. The study concluded that supervisor support and career mentoring significantly affect succession planning in the Nigerian public sector and this study recommended that organizations particularly Nigerian universities should embrace supervisor support and career mentoring for effective succession planning.