Successive administrations in Nigeria have developed a number of programmes and policies (Universal Basic Education (UBE), National Immunization Coverage Scheme (NICS), Midwives Service Scheme (MSS) and Structural Adjustment Progranme (SAP) etc.) aimed at harnessing the positive influence of trade openness on human capital investment in the country. In spite of these, human capital in Nigeria is grossly under developed. This paper examines the impact of tr\ade openness on human capital investment in Nigeria between 1981 and 2020. The study employed Vector Auto Regression (VAR) modeling techniques for the analysis. Human capital investment was proxied by total government expenditure in health and education (dependent variable) while trade openness was measured by trade openness index (explanatory variable). Per capita electricity consumption and exchange rate served as check variables. Human capital investment showed strong endogenous impact (strong influence) on its self while trade openness and per capita electricity consumption exhibited strong exogenous impact (weak influence) on human capital investment throughout the forecast period. The study recommended that, since trade openness in Nigeria is crude oil centered, government should invest more revenue from the sales of crude oil in human capital development for trade openness to have any significant impact on human capital investment in Nigeria.