Background and objective: The underlying mechanisms for the well-established link between social support and depression remain less understood. This study examined the mediating role of sedentary behaviour (SB) in the relationship between social support (SS) and depression among individuals with diabetes. Methods: A total of 250 consenting individuals with diabetes attending endocrinology clinic in a Nigerian tertiary hospital were recruited. The International Physical Activity Questionnaire Short Form, Multidimensional Scale of Perceived Social Support, and Center for Epidemiologic Studies Depression Scale were used to collect data on SB, SS and depression respectively. Mediation analysis was performed with hierarchical multiple regression and PROCESS Macro for SPSS. Alpha level was set at p < 0.05. Results: The prevalence of depression among diabetic patients was 30.8%. Social support had a significant negative association with depression and SB, while SB was positively associated with depression (P < 0.001). The results showed that SB was a mediator between social support and depression (a*b = -0.151; BCa 95% CI: -0.207 ~ -0.102). Conclusion: The prevalence of depression was high among Nigerian diabetic patients. In addition, SB has a mediating role in the relationship between social support and depression indicating that SB could reinforce the positive effect of social support on depression
