The study investigated the impact of fiscal policy on gross capital formation in Nigeria using time-series data from 1986 to 2021. Relevant conceptual and empirical literatures were reviewed. Fiscal policy was disaggregated into total government revenue, total government expenditure, total government borrowing, and government budget deficit against private investment proxy by gross capital formation. An ex-post facto research design was adopted. Data were sourced on these variables from the Central Bank of Nigeria Statistical Bulletin, 2021, World Development Indicators 2021. Descriptive statistics, the Augmented Dickey-Fuller unit root test, the Johansen cointegration test, and the Error Correction Model (ECM) were employed in analysing the data. The result of the descriptive statistics indicated that all the variables were normally distributed. While the Augmented Dickey-Fuller (ADF) test statistics showed that all the variables used in this study were stationary at first. The results of the Johansen cointegration tests showed a long-run relationship between dependent and the explanatory variables in each of the models. The results of the error correction model met the condition of the error correction term. The study found that total government revenue has a positive and statistically significant impact on gross capital formation in Nigeria. Also, total government expenditure has a positive impact on gross capital formation in Nigeria. While total government borrowing has a negative and insignificant impact on gross capital formation in Nigeria, More so, the government budget deficit has a negative and significant impact on gross capital formation in Nigeria. The study therefore concludes that there is a positive impact between fiscal policy and capital formation in Nigeria. The study therefore recommends concerted efforts from relevant authorities to channel funds towards capital projects and also restructure their tax systems to prevent the negative effects of public debt and deficit financing on private investment.