Young children with early emotional, behavioral, and regulatory problems are at risk for long-term behavioral and academic challenges. This study examined the associations between O-classroom quality (i.e. emotional, organizational, and instructional supports) and problem behavior in six-year-old children who attend preschool. A correlation study design, under a quantitative approach, was used. Participants included 503 children (244 male and 259 female) living in the Wolaita communities of Southern Ethiopia. The Classroom Assessment Scoring System (CLASS; Pianta, La Paro, & Hamre, 2008) was used to assess classroom quality across three domains: emotional support, classroom organization, and instructional support by certified observers. The O- classrooms were observed three times during six cycles, twice in the first, second, and third observation. Furthermore, the Preschool and Kindergarten Behavior Scales (PKBS, Merrell, 1994, 2002) were used to measure children's problem behavior. Hierarchical linear modeling results showed that the O-classroom quality score had a significant negative correlation with problem behavior. Analyses revealed that the combined effects of observed O- classroom quality explained a 73% variance in children's problem behavior. Taken together, these findings indicate that classroom organization and emotional support significantly and negatively predicted children's problem behavior. Areas of further research and implications for policy and practice are advanced based on the major findings.