Mental illness and substance abuse makes up the leading cause of disability among adolescents globally, and yet adolescent mental health is an understudied area in developing countries. Using data from South Africa, this paper provides the first nationally representative estimates of the inter-generational transmission of depressive symptoms in Sub-Saharan Africa, using data from 2012. Using a longitudinal household survey, we find that one-third of South African adolescents will suffer from depressive symptoms if either parent does so - and that parental mental health is the single largest determinant of child mental health. We exploit the exogenous variation in the roll-out pattern of an unconditional cash transfer in South Africa, and find that the South African child support grant is associated with a reduction in the intergenerational transmission of depressive symptomatology to adolescent children by more than forty percent. This potentially mitigating effect is larger for female adolescents, who are more likely to be affected negatively by parental mental illness than male adolescents. This is not to deny the importance of the shared household environment on the mental health of both adolescents and parents, but in the absence of sufficient treatment for mental illness among South African youth, the child support grant appears to play a crucial role in supporting mental health outcomes amongst low-income adolescents.