Despite notable reductions in under-five mortality globally, environmental risks like household air pollution (HAP) remain major contributors to child deaths, especially in low- and middle-income settings. In Kyrgyzstan, where many households still rely on solid fuels for cooking and heating, the relationship between HAP and under-five child mortality has not been well examined. We analyzed data from the 2023 Kyrgyzstan Multiple Indicator Cluster Survey (MICS), a nationally representative cross-sectional survey with retrospective birth history data. The study population included live births in the five years preceding the survey. Household fuel type, measured at interview, was classified as clean or polluting based on cooking and heating fuels. Under-five mortality was examined using Cox proportional hazards regression with reconstructed survival time from birth histories. The primary model incorporated MICS sampling weights, stratification, and clustering to account for the complex survey design. Kaplan-Meier curves were used to compare survival probabilities by HAP exposure group, and multivariable models adjusted for child, maternal, and household-level covariates. Among 3,056 children, 88% lived in households using polluting fuels for cooking or heating. Under-five survival was significantly lower among children exposed to HAP, with a survival probability of 97.6% in polluting-fuel households versus 98.9% in clean-fuel households at 60 months (log-rank p = 0.004). In the primary survey-weighted Cox model, exposure to polluting fuels was associated with approximately two-fold higher under-five mortality (hazard ratio [HR] = 2.07; 95% CI: 1.07-4.01). Higher birth order was associated with increased mortality, while female sex and older maternal age were associated with lower mortality hazard. Polluting household fuel use was associated with a higher under-five mortality hazard in Kyrgyzstan. Because household fuel type was measured at the survey interview, these findings should be interpreted as associations rather than causal effects. Nevertheless, the results suggest that household energy conditions may be relevant to child survival and support cautious policy consideration of clean cooking and heating strategies, particularly in rural and mountainous areas. Future prospective studies with direct exposure measurement are needed to clarify exposure timing, causal pathways, and the potential mortality benefits of household energy interventions.