Purpose: This study examines the short-run and long-run impact of the expansionary fiscal policy on economic growth in Zambia from 1991 to 2021. Materials and Methods: The study employs the Vector Error Correction Model (VECM) and Auto Regressive Distributed Lag (ARDL) Models to examine the short-run and long-run impact of total public expenditure, total tax revenue and total public debt time series data on the gross domestic product (GDP) of Zambia from 1991 to 2021. The Keynesian theory informed our study, which presupposes that the unemployment problem might be solved by boosting government spending on consumption and that government spending was an exogenous factor that contributed to economic growth (Keynes, 1936; Singh & Sahni, 1984). Findings: Both the VECM and ARDL Models show the existence of statistically significant long-run cointegration among public expenditure, external debt, tax revenue and GDP. Specifically, VECM estimates show that for a 1% increase, Tax revenues have a positive long-run significant effect on Zambia’s economic growth of 3.36%, while external debt and public expenditure have significant negative effects on the economic growth of 1.17% and 0.003% in Zambia respectively. The ARDL model estimates indicate that, in the short run, an increase in tax revenue of 1% increases GDP growth by 1.92%, while a rise in government expenditure and external debt by 1% results in a decline in Zambia’s economic growth by 0.003% and 6.14% respectively. Implications to Theory, Practice and Policy: Given the foregoing findings, the therefore study recommends that the Government of Zambia should widen the tax base to mobilize more tax revenues and reduce the budget deficits emanating from high government expenditures. External public debt should also be reduced.