This study investigated the impact of internally sourced revenue optimality on Nigeria’s national economic development. Internally generated income had traditionally been the mainstay revenue source for the economic development of countries, but it has long been a subject of worry for Nigeria's national economic development, considering how effectively internally generated income is being used for the progress of the country. We adopted an ex-post facto research design, using annual time series data covering a period of 31 years (1992Q1-2022Q4), sourced from the Central Bank of Nigeria Statistical Bulletin and the National Bureau of Statistics. Two variables were considered, the dependent variable of the study (National economic development) proxied with Real Gross Domestic Product (RGPD) and the independent variable (internally sourced revenue) using the total internally sourced revenue that accrued to the federal (FIGR), States and Federal capital territory (SFCTIGR), and Local government (LIGR) as the explanatory variables for the study. The study found that internally sourced revenue positively affects Nigeria’s national economic development and that the period experienced unstable internally generated revenue and weak optimal use of the revenue. The study concluded that internally sourced revenue and optimal utilization of internally sourced revenue affect national economic development. Based on the findings, the study recommended that the Nigerian government should optimally utilize internally sourced revenue to enhance the national economic development of Nigeria.