Acute respiratory infections (ARI) are the most common infectious diseases that cause death in children under five in the world. In Indonesia, the incidence of ARI is influenced by nutritional status, exclusive breastfeeding, immunization, economy, population and geography. The purpose of the study was to determine the risk factors for the incidence of ARI in children under five in the working area of the Poasia Public Health Center, Kendari City. This study uses a casecontrol approach. The research sample amounted to 52 mothers who had children under five who suffered from ARI and 52 mothers who had healthy toddlers (control). Data collection using a purposive sampling technique. Data were analyzed using the Chi Square test and logistic regression. The results showed no difference in the distribution of characteristics of the case group and the control group, except for the education level where the percentage of respondents with higher education (high school and undergraduate) in the control group was higher than the case group (94.2% vs. 59.6%). This study also found that low level of knowledge (score <13), poor room humidity (<40% or >70%), poor ventilation (<10% room floor area) and dense occupancy density (< 8 m2 per 2 occupants) is a risk factor for the incidence of ARI in children under five in Poasia District, Kendari, Southeast Sulawesi. The increased risk of ARI in children under five for each variable was 5. 50, 5.13, 2.63, and 2.44 times, respectively. The most dominant variable as a risk factor for the incidence of ARI is room humidity with an OR value of 7.567 times. The study concludes that the mother's level of knowledge, room humidity, ventilation and occupancy density are risk factors for the occurrence of ARI in children under five in Poasia District,