Background: Pneumonia is the second highest cause of under-five mortality in Indonesia. This study aimed to analyse the risk factors for pneumonia among under-fives in Wajo Regency. Methodology: This type of research was a quantitative study using a case-control study design. The population was all children in the working areas of Salewangeng Health Centre, Penrang Health Centre, and Belawa Health Centre. The sample size was 224 children consisting of 112 cases and 112 controls. The odds ratio test and logistic regression were used to evaluate the data. Results: Risk factors associated with pneumonia were under-five nutritional status (OR=3.563; 95%CI=1.57-8.65; p=0.0008), indoor smoke exposure (OR=5.852; 95%CI=2.88-12.36; p=0.000), maternal age (OR=2.575; 95%CI=1.45-4.58; p=0.0005), and number of children in the family (OR=3.133; 95%CI=1.65-6.05; p=0.0002). Conclusions: The most influential risk factor for under-five pneumonia was indoor smoke exposure. The probability of pneumonia among under-fives who were exposed to indoor smoke, had a maternal age 30 years, and had poor nutritional status was 89.8%. It is recommended for the community to reduce smoking activities in the house and reduce the use of mosquito coils to prevent smoke exposure to children at home.