Public debt is one of the key economic variables in developing countries, particularly resource-dependent economies such as Iran. This study aims to examine the impact of natural resource rents (disaggregated into oil, natural gas, coal, minerals, and forests) on the level of Iran’s government public debt and its cyclical behavior over the period 1981–2023. Using the ARDL econometric approach and incorporating the interactive effects of various rents and business cycles, six separate models were estimated. The results indicate that total natural resource rents, particularly oil, directly reduce public debt in both the short and long run. Additionally, debt behavior is predominantly procyclical; that is, it increases during economic booms and decreases during recessions. Regarding the role of resource rents in debt cyclicality, major fossil rents (oil, coal, and gas) weaken procyclicality and have the potential to induce countercyclical behavior, while mineral rents exacerbate it. Forest rents play a positive and more stable moderating role in reducing cyclical fluctuations. The speed of adjustment to long-run equilibrium is slower in models based on fossil rents, indicating greater persistence of oil and gas shocks on debt. Control variables such as inflation (debt-reducing via inflation erosion) and trade openness (with dual effects) also play significant roles. These findings align with the resource curse theory and suggest policy measures focusing on diversification, stabilization funds, and institutional strengthening to enhance fiscal sustainability.