Research Findings: This study examined the extent to which observed classroom quality and teacher stress are associated with children's social competence in classrooms of 6-year-old children (kindergartners in Finland). Assessments of academic pre-skills were available for a total of 1,268 children, and kindergarten teacher ratings of social competence were available for a total of 1,222 children. The kindergarten teachers (N=137) also provided ratings of their work-related stress. Observations of classroom quality (i.e., emotional and instructional support and classroom organization) were conducted in 49 kindergarten classrooms using the Classroom Assessment Scoring System. The results of multilevel modeling showed that the higher the observed instructional support in the classroom and the lower the level of stress a teacher reported, the more empathy and less disruptiveness the children displayed in that particular classroom. High teacher stress was also associated with higher impulsivity and lower cooperation skills among the children. Practice or Policy: The results emphasize the importance of a teacher's well-being and instructional quality in kindergartens for children's social skills. (author abstract)