The article explores how public debt in Nigeria affects economic growth by looking at its impact on investment. Using data from 1981 to 2019, the study found that external debt and investment are good for economic growth, while domestic debt and external debt payments can hinder growth. It suggests that keeping domestic debt investment above 25.41% is crucial to avoid an economic downturn, but investing more than 24.55% of external debt can harm the economy. The research also warns that increasing domestic debt investment is beneficial, but relying too much on external loans can be damaging. Monitoring external debt investment is recommended to ensure it is used effectively and not for personal gain.