Pneumonia is an important cause of mortality and morbidity in infants. However, information of risk factors for pneumonia in children aged <6 months is limited. This study aimed to evaluate the risk factors and their contribution to infantile pneumonia in a large population-based survey. Of 24,200 randomly sampled main caregivers invited, 21,248 (87.8%) participated in this study. A structured questionnaire was used to interview the main caregivers. Information regarding whether hospitalization was required, family environment, and medical history were obtained. The prevalence of pneumonia was 0.62% in our study cohort. Multivariate logistic regression analysis showed that preterm birth, congenital cardiopulmonary disease, antibiotic use during pregnancy, maternal overweight, daily prenatal exposure to environmental tobacco smoke, maternal smoking during pregnancy, and visible mould on walls at home are risk factors associated with infantile pneumonia. Further study is warranted to investigate the causality and mechanisms of these novel factors.