This study examines pension sector reform and investment expansion under the administration of President Bola Ahmed Tinubu and the implications for financial system stability and economic growth in Nigeria. Looking at three key issues: the extent to which post-2023 pension regulatory adjustments influence economic growth, the effect of pension investment expansion on financial stability, and the relationship between pension asset growth and investment diversification in Nigeria. The study adopted a quantitative research approach using time-series data, which were obtained from relevant institutional sources that include the National Pension Commission and the Nigerian Bureau of Statistics. The data were analysed using Ordinary Least Squares (OLS) regression techniques to estimate the relationships among the variables. To ensure the reliability of the empirical results, several diagnostic tests were conducted, including unit root tests, cointegration analysis, multicollinearity tests, and heteroskedasticity tests. The research findings show that the changes in pension regulations made since 2023 have positively impacted economic growth; the expansion of investment opportunities in the pension sector plays a crucial role in enhancing financial stability by improving liquidity, deepening capital markets, and providing a reliable source of institutional investment. The study concluded that reform in the pension sector and the growth in investments have reinforced the Nigerian pension industry’s role as a vital tool for mobilising domestic savings, fostering capital market development, and supporting sustainable economic growth. Therefore, the study recommends enhanced regulatory frameworks, diversified investment strategies, broadening of pension coverage, and creating reliable infrastructure investment options.