This study uses annual data from 1981 to 2019 to evaluate the ideal public debt threshold that would be consistent with Nigeria's long-term growth goal. It showed overall support for an inverted U-Shaped relationship between the three categories of public debt—domestic, external, and total—and economic growth. For total public debt as a percentage of GDP, the result indicates a threshold level of 41 % (as the optimal debt benchmark). The implication of this finding is that debt accumulation in excess of the estimated threshold levels could hurt economic growth. Against the general notion, the study found no support for external debt accumulation opportunities. The policy import of our result is, therefore, the need for government to exercise caution in further debt accumulation, the absence of such a caution in debt accumulation could result in debt levels that are inconsistent with the country’s growth objective.