Indoor air pollution poses a significant threat to child wellbeing, as children typically spend a considerable amount of time indoors and are more vulnerable to air pollution than adults. Cooking with polluting fuels, including biomass (wood, animal dung, and crop waste), lignite coal, charcoal, and kerosene, represents a major source of indoor household air pollution. This study evaluates the impact of indoor household air pollution on morbidity in children under 5 years of age in Pakistan using quasi-experimental methods. The results indicate that 49% of households in Pakistan primarily rely on polluting fuel for cooking, while the remaining 51% use cleaner fuels such as natural gas, LPG, electricity, or biogas. The empirical findings reveal that the probability of Acute Respiratory Infection (ARI) symptoms in children increases by 2.40 percentage points if the household uses polluting fuel for cooking. Moreover, the probability of ARI symptoms in children decreases by 1.99 percentage points if the household has a separate kitchen room for cooking. Additionally, the probability of ARI symptoms in children decreases by 2.53 percentage points if there is no tobacco smoking inside the house. We also find empirical evidence that the probability of mortality in children increases by 1.42 percentage points if the household uses polluting fuel for cooking. The findings of this study underscore the crucial role of household behavior in averting exposure to indoor household air pollution and reducing the associated health risks.