The study focused on the determinants of government agricultural expenditure in the long and short run from 1999-2020 using Vector Error Correction Model approach. Annual time series data on agricultural GDP, agricultural expenditure, inflation rate, exchange rate, interest rest, private investment, public investment and foreign direct investment collected from the records of Central Bank of Nigeria and National Bureau of Statistics database were analyzed using inferential statistics (ADF, Johansen co-integration and VECM). The results showed that all the variables co-integrate and were stationary at first difference. In the long run, inflation (1.118415) and private investment (0.004239) were the significant and important variables that determine agricultural expenditure. The coefficient of multiple determination (R2) was 0.925, indicating that 92.5% variation in agricultural expenditure was explained by the variables. The Error correction Term is statistically significant and negative (-0.0278) in the short run indicating a slow speed of adjustment of variables towards equilibrium. In the short run, inflation, private investment and public investment were the important variables that influenced government expenditure. The study concludes that inflation, private and public expenditures influenced government agricultural expenditure significantly and therefore recommend friendly policies to curtail inflation, conducive environment to catalyze private investment and stimulation of public investment to boost agricultural growth.