To estimate the effect of income change on difficulty accessing food since the COVID-19 pandemic for South African youth and evaluate whether this effect was modified by receiving social grants. A cross-sectional, online survey was conducted between December 2021 and May 2022. Primary outcome was increased difficulty accessing food since the COVID-19 pandemic. Income change was categorised as 'Decreased a lot', 'Decreased slightly' and 'Unchanged or increased'. Multivariable logistic regressions were used, with an interaction term between social grant receipt and income change. eThekwini district, South Africa. Youth aged 16-24 years. Among 1,620 participants, median age was 22 years (IQR 19-24); 861 (53 %) were women; 476 (29 %) reported increased difficulty accessing food; 297 (18 %) reported that income decreased a lot, of whom 149 (50 %) did not receive social grants. Experiencing a large income decrease was highly associated with increased difficulty accessing food during the COVID-19 pandemic (adjusted OR [aOR] 3·63, 95 % CI 2·70, 4·88). The aOR for the effect of a large income decrease on difficulty accessing food, compared to no income change, were 1·49 (95 % CI 0·98, 2·28) among participants receiving social grants, and 6·63 (95 % CI 4·39, 9·99) among participants not receiving social grants. While social grant support made a great difference in lowering the effect of income decrease on difficulty accessing food, it was insufficient to fully protect youth from those difficulties. In post-pandemic recovery efforts, there is a critical need to support youth through economic empowerment programming and food schemes.