PURPOSE: Under-five mortality is a key public health indicator, highly responsive to preventive interventions. While global efforts have made strides in reducing mortality rates in this age group, significant disparities persist, particularly in Sub-Saharan Africa. This study aimed to systematically review the factors influencing under-five mortality in Africa, focusing on sociodemographic factors and health-related determinants. METHODS: A systematic review was conducted adhering to PRISMA guidelines. Studies were identified from a range of well-established indexed academic databases. Keywords and Boolean operators facilitated relevant study retrieval. Only articles published in English, Portuguese, or Spanish between January 2013 and November 2024, in peer-reviewed journals, were included. Methodological quality assessment utilised the Joanna Briggs Institute tool. RESULTS: Of the 602 studies identified, 39 met the inclusion criteria. Key determinants of under-five mortality included socioeconomic factors such as poverty and maternal education, along with maternal age extremes, multiparity, inadequate prenatal care, and low birth weight. CONCLUSION: Addressing social disparities, particularly through enhanced maternal education and improved access to primary healthcare, is critical in reducing under-five mortality in Africa. The findings underscore the importance of targeted interventions that address both social and healthcare-related factors to mitigate child mortality in the region. WHAT IS KNOWN: •Under-five mortality in Sub-Saharan Africa is primarily driven by preventable infectious diseases, such as diarrhoea, pneumonia, malaria, and HIV/AIDS, compounded by malnutrition and inadequate healthcare infrastructure. •Socio-economic factors, including poverty, maternal education, and limited access to quality healthcare, are consistently identified as key determinants of high child mortality rates in the region. WHAT IS NEW: •This review applies the Mosley and Chen framework to categorise the determinants of under-five mortality into distal, intermediate, and proximal factors, providing a structured understanding of their interconnections. •The findings underscore how socio-economic conditions, maternal education, and healthcare access interact to influence child survival outcomes in Sub-Saharan Africa, offering valuable insights for region-specific public health interventions.