The research work examined the effect of financial deepening on the Nigerian economic growth from 1999-2022. The specific objectives of the study assessed the relationship between financial deepening variables such as money supply, and private sector credit, economic development proxied by per capita income over the period. Ex-post facto research design was the adopted research design for this study. The study utilized secondary data from the CBN annual reports and statistical bulletin. The data collected were presented in tables. Hypotheses were tested using ordinary least square (OLS) regression techniques. The study found among other things that revealed that there is a significant and positive relationship between money supply and economic development in Nigeria, there is a significant and positive relationship between private sector credit and economic development in Nigeria. Based on the Findings, the study recommend that Improving access to credit for small and medium-sized enterprises (SMEs) and individuals, especially in underserved rural areas, to stimulate entrepreneurial activities and investment, leading to economic development.