The increasing reliance on public external debt stocks in Africa and other developing countries has raised the question of debt sustainability, especially in the face of Covid-19, which has forced many counties (both developed and developing) into an unforeseen and unplanned recession. This study contributes to the literature on debt sustainability by examining the effect of public debt on capital formation in Sub-Saharan Africa (SSA) from 2000 to 2008 using the pooled mean group estimation approach. The debt variables considered are external debt stock, debt service on external debt, and interest payment on external debt. Consistent with the overhang theory, our results show that increasing external debt stock and interest payment on external debts only have a marginal impact on capital formation in the short run and exerts a serious negative effect in the long run. Our results also show that debt service burden has a positive effect on gross fixed capital formation in the long run. Therefore, we argue that despite being faced with a huge debt service burden resulting from large external debt stock, SSA countries are not neglecting investments in critical infrastructures needed to drive economic growth. However, we recommend that increasing government revenue base, minimizing economic waste associated with public expenditure, and intensifying negotiations for debt relief may be a plausible way out.