"Research Findings": Early childhood workers (ECW's) play a pivotal role in shaping children's emotional competence. This study examined the efficacy of Tuning in to Kids for Kindergarten Teachers (TIK-KT) used with CLASS observations to improve ECW's emotion socialization, kindergarten emotional climate and children's functioning. Five hundred and forty-eight ECW's and leaders from 49 Norwegian kindergartens (children 1-5?years) were cluster randomized into intervention or control. Senior employees from intervention kindergartens received a two-day TIK-KT training, ECW's participated in a one-day training to learn emotion socialization skills and then ECW's received supervision to use emotion coaching with the children. Baseline and 10-month follow-up measures included questionnaires with ECW's and parents, and observations of kindergartens. Compared to controls, intervention ECW's reported a significant decrease in emotion dismissing and distraction, and a significant increase in emotion coaching. Intervention but not control kindergartens were observed to have significantly increased positive climate, teacher sensitivity, regard for student/child perspective, and behavior guidance. There was no change in parent reported child behavior; however, floor effects at baseline and a short follow-up during the COVID pandemic may have made change difficult to detect. "Practice or Policy": These findings provide preliminary support for use of TIK-KT as a universal intervention.