Income inequality has always been regarded as one of the most significant political, social, and economic concerns worldwide. It is also one of the challenges that has drawn the attention of policymakers and economic authorities in Iran in recent decades. Therefore, identifying the factors influencing income distribution is crucial in policymaking. Accordingly, the present study seeks to empirically examine the relationship between fiscal policy (government expenditures, tax rates, and financial development) and income inequality (Gini coefficient) using the Markov-Switching approach, with quarterly data from 2001 to 2022. The results of the study indicate that the hypothesis of symmetry regarding the effects of financial development, government expenditures, and income taxes on income distribution in Iran during recessions and booms can be rejected. The impact of financial development, government expenditures, and income taxes—as indicators of fiscal policy—on income distribution is greater during booms than during recessions. These findings suggest that fiscal policy has asymmetric effects on income distribution in Iran.