BACKGROUND: The role of biological factors such as foetal haemoglobin in modifying the severity of Sickle Cell Anaemia (SCA) has been extensively investigated. However, the phenotypic variability of SCA cannot be explained by genetic factors alone. Hence, the need to determine other correlates of SCA severity such as perceived stress and social support. METHODS: This was a hospital-based cross-sectional study involving 60 participants aged 8-17 years selected using simple random sampling technique. Standard rating scales (i.e., SCA scoring system, perceived stress scale, and child and adolescent social support scale) were used to assess the severity of SCA, perceived stress and social support, respectively. Foetal haemoglobin (HbF) was estimated using high performance liquid chromatography. The psychosocial predictors of sickle cell severity were analyzed using multivariate linear regression. RESULTS: There was a negative moderate significant correlation between SCA severity and domains of social support: parents' (rho = -0.30, p = 0.03) and classmates' (rho = -0.50, p <
0.001). Of all the variables studied, only classmates' perceived social support emerged as the significant predictor of SCA severity when other confounders such as HbF were controlled for (β = -0.37, t = 2.41, p = 0.02). CONCLUSION: The findings of this study support the available literature on the mediating effect of social support on SCA severity. These findings buttress the need for clinicians to consider psychosocial methods (e.g., family and classmates' support) in improving disease outcomes.