Background: Globally, pneumonia is an infectious disease with high morbidity and mortality rates. It causes one of five deaths in children under five years old worldwide. Approximately 61 million new cases of pneumonia in Sout East Asia occur annually. This study aimed to examine risk factors of pneumonia among children under five in Karanganyar, Central Java. Subjects and Method: This was an analytic observational study with case control design. The study was conducted in Karanganyar District, Central Java, from October to November, 2017. Study subjects were selected by fixed disease sampling consisting of 68 children under five years old with pneumonia and 136 without pneumonia. The dependent variable was pneumonia. The independent variables were nutritional status, exclusive breastfeeding, maternal stress, type of labour, maternal education, maternal job status, family income, number of children, quality of house, quality of environment, and indoor smoke exposure. The data was collected by questionnaire and analyzed by path analysis. Results: The risk of pneumonia increased with indoor smoke exposure (b= 2.57; 95% CI= 1.54 to 3.60; p< 0.001), number of children ≥3 (b= 1.34; 95% CI= 0.45 to 2.24; p= 0.003), and maternal stres during pregnancy (b= 1.02; 95% CI= 0.16 to 1.88; p= 0.019). The risk of pneumonia decreased with good house environment (b= −0.95; 95% CI= −1.80 to -0.09; p= 0.030), healthy behavior (b= −1.21; 95% CI= −2.09 to −0.33; p= 0.007), and good nutritional status (b= −1.91; 95% CI= −2.92 to −0.90; p<0.001). The risk of pneumonia was indirectly affected by exclusive breastfeding, history of Caesarean section , maternal education, maternal working outside the house, family income, and good quality of house. Conclusion: The risk of pneumonia increases with indoor smoke exposure, but decreases with good house environment, healthy behavior, and good nutritional status.