This study examined the correlation between foreign investment inflows and stock market capitalization in Nigeria, using an ex-post facto research approach. The population consisted of the Nigerian economy, and a sample was taken from the available data to capture foreign direct investment (FDI) flows, foreign portfolio investment (FPI) flows, and stock market capitalization from 1994-2022. Judgmental sampling was employed to select variables, and secondary data from the Central Bank of Nigeria (CBN) annual reports for 1994-2022 were utilized. Time-series data from 1994 to 2022 were analyzed using Eviews 9.0 software, employing cointegration tests, normality tests, descriptive statistics tests, and regression analysis. The cointegration tests revealed no evidence of a long-term equilibrium relationship among the variables. At the same time, regression analysis indicated positive and significant relationships between foreign portfolio investment and foreign portfolio investment flows with stock market capitalization in the short term. Therefore, policymakers are recommended to create an environment conducive to attracting and retaining foreign investment, focusing on measures to encourage and sustain FPI inflows, such as enhancing market liquidity and improving investor protection mechanisms.