This study examined the determinants of government expenditure in Southwest Nigeria. The study adopted ex-post facto research design and it covered 10 years, spanning from 2010 to 2019. The panel data used was sourced from the CBN statistical bulletin (2019) and the annual budget of each of the sampled states. Panel data estimation techniques were used and based on the most consistent and efficient estimation, it was discovered that internally generated revenue exerts a positive significant effect on both capital and recurrent expenditure to the tune of1.315 (p=0.000 < 0.05) and 0.670(p=0.001 < 0.05) respectively. It was equally discovered that statutory allocation exerts a positive but insignificant effect on both capital and recurrent expenditure for the period covered to the tune of 0.34 (p=0.236 > 0.05) 0.389 (p=0.065 > 0.05) respectively. Also, it was discovered that domestic debt exerts a negative insignificant effect on capital expenditure to the tune of -0.061 (p=0.733 > 0.05). Finally, domestic debt has a positive but insignificant effect on recurrent expenditure to the tune of 0.109 (p=0.352 > 0.05). It was established that internally generated revenue, statutory allocation and domestic debt are the determinant factors of public expenditure across all the states in the Southwest region of Nigeria. Thus, it was recommended that available revenue should be judiciously utilized on the pressing needs of the state. While revenue is needed for the functionality of the government, state governments are urged to embrace more capital projects through which additional revenue might be generated.