This research looked at how internal and external sources of financing affected the Nigerian economic growth from 1981 to 2020. Using sourced data from the Statistical Bulletin of the Central Bank of Nigeria, domestic savings and internal debt were measures for internal financial sources, foreign debt and foreign direct investment were measures of external financial sources, and real GDP was used as the measure for economic growth. An Error Correction Mechanism was used to analyze the data. The findings showed that domestic savings have a negative impact on the economic growth of Nigeria; however, this impact was statistically insignificant. Domestic debt, on the other hand, positively and significantly impacts economic growth in Nigeria. Although foreign direct investment positively affected the Nigerian economic growth, foreign debt has a negative effect. However, both of these impacts were statistically insignificant. As a result, it was found that the internal funding of economic growth is more efficient than the external finance. Also, internal sources of funding have a bigger influence on economic growth than external sources of funding, according to the findings. Keywords: Domestic Savings, Internal Debt, Foreign Debt, Real Gross Domestic Product DOI: https://doi.org/10.35741/issn.0258-2724.58.2.61