This study estimated the direct and indirect contributions of mentorship and institutional support (IS) to academic staff's research productivity (RP) at a public university in Cross River State. Two mediator variables--collaboration and institutional culture (IC), were introduced to determine their roles in the nexus between the predictors and the criterion variables. The quantitative research method was adopted following the correlational research design. "Career Empowerment and Research Productivity Questionnaire (CERPQ)" was used for data collection after validation by experts and reliability test. Three hundred twenty-seven copies of the CERPQ were administered, but 303 were retrieved. Mediation-based analysis was performed using structural equation modelling following the research questions and hypotheses. Amongst others, findings revealed that mentorship had a non-significant negative contribution to the RP of academic staff; mentorship only promoted RP among academic staff when it was followed by positive IC and collaboration. IS had a non-significant positive contribution to the RP of academic staff. The joint mediation of collaboration and IC was significant in the nexus between mentorship and RP and between IS and RP of academic staff in the public university. Collaboration was the most important factor directly associated with the RP of academic staff and also partially mediated the contributions of other variables (such as mentorship and IS) to the RP of academic staff. The results of this study can be useful for universities seeking to enhance the research productivity of their academic staff. The study highlights the importance of considering multiple factors that may influence research productivity and suggests that institutions should prioritise fostering a supportive and collaborative environment for academic staff to maximise their research productivity. The study can also inform the development of mentorship programmes and the creation of institutional policies that support and promote research productivity.