The purpose of this study is to examine the effect of external public debt on economic growth and to assess the debt sustainability of twenty-four SSA countries over the period 2000–2017 using descriptive trend analysis and panel data analysis. The study found that external public debt has a negative and significant effect on the economic growth of low income SSA countries. The study also found that the external debt of low income SSA nations is unsustainable. In light of these findings, selected SSA countries should adopt a balance between external and domestic debt to ensure sustainable economic growth. They should also implement measures to promote export and expand domestic investment.