Background <p>Indoor air pollution is a major public health issue and contributor to acute respiratory infections among under-five children in low- and middle-income countries. Although numerous studies have explored this association, existing evidence is fragmented, varies across settings and lacks comprehensive synthesis. This study addresses this gap by quantifying the pooled effect size of the association between indoor air pollution exposure and acute respiratory infection and identifying determinant factors among under-five children in low- and middle-income countries.</p> Methods <p>The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guideline was used for this review. The study reviewed 36 research articles obtained from databases including PubMed, ScienceDirect, HINARI, and Google Scholar from January 1, 2015, to September 1, 2024. Data were extracted using Microsoft Excel and then analyzed in STATA-17 software. The Joanna Briggs Institute quality appraisal tool was utilized to evaluate the included studies. A random effects model was applied to calculate the pooled effect size, while publication bias was examined using funnel plots and Egger’s regression test. Additionally, subgroup analysis, meta-regression, and sensitivity analysis were performed.</p> Results <p>The pooled effect size of acute respiratory infection among under-five children associated with exposure to indoor air pollution was 13.56% (95% CI: 11.88–15.25), with high heterogeneity (I² = 99.9%, p-value &lt; 0.001). Exposure-related factors, including absence of a kitchen window (OR = 4.47, 95% CI: 1.66–7.28), use of traditional stoves (OR = 2.53, 95% CI: 1.02–4.03), secondhand smoke exposure (OR = 1.19, 95% CI: 1.06–1.32), and use of unclean fuels (OR = 1.16, 95% CI: 1.07–1.25) were significantly associated with acute respiratory infection among under-five children. In addition, child health and nutritional factors such as diarrhea (OR = 3.76, 95% CI: 3.51–4.01), and stunting (OR = 1.16, 95% CI: 1.02–1.31) were also linked to increased risk. Furthermore, demographic and household characteristics, including child’s age, sex, wealth index, lack of separate kitchen, presence of children near in stove during cooking and birth order were identified as significant predictors.</p> Conclusions <p>This study highlights a significant association between indoor air pollution and acute respiratory infection in under-five children. Targeted interventions, including the promotion of clean cooking fuels, smoke-free households, and improved household ventilation are essential.</p>