Purpose: Given declining tuition funds and government grants, Kenyan universities need to develop strategies, including increased research grants and collaborations, to diversify their income sources. Well-managed doctoral students can boost a university's teaching and research outputs. However, numbers of students enrolled in doctoral programmes at Kenyan universities are low, and graduation rates and time-to-graduate statistics are disturbing. Research undertaken elsewhere underline the important role played by supervisors and peers in facilitating students' sense of belonging and their success. Therefore, this study aims to investigate the influence of supervisory and peer support on PhD students' sense of belonging and their success at Kenyan universities. Design/methodology/approach: In this cross-sectional study, data were gathered through an online questionnaire from 614 students admitted to doctoral programmes at Kenyan universities between 2010 and 2018. We used multi-item scales to collect data on PhD students' self-efficacy, supervisory and peer support and a sense of belonging. Findings: Structural equation modelling results revealed that PhD students' modes of study and self-efficacy were significantly associated with the quality of supervision, peer support and a sense of belonging. However, only age, a sense of belonging and the quality of supervision were directly linked to their success. Originality/value: This study contributes to the literature on doctoral-level education, responding to the need for research on the influence of relationships with supervisors and peers on PhD students' sense of belonging and their success, especially in developing countries.