This study empirically examined the relationship between Domestic Private Investment, lending Interest Rate and taxes in Nigeria from 1999 to 2020. The objectives of this research are to determine the effect of interest rate on private domestic investment and to determine the effect of taxes on private domestic investment. In order to achieve these objectives relevant data for the study were obtained from FIRS and WDI. Unit root test (ADF), multiple regression analysis model (OLS) and other post estimation tests were used in order to estimate the relationship dependent and independent variables. The unit root test shows that dependent variable (DPI) is stationary at level while the explanatory variables (LIR and TAXES) become stationary at first difference. The regression result shows an inverse relationship between domestic Private Investment and lending interest rates in Nigeria while the relationship between domestic Private Investment and taxes is positive above all, the explanatory variables are found to be significant in influencing domestic private investment in Nigeria. Other post estimation tests conducted shows that the model is fit.