We assessed impacts on classroom quality and on 5 child language and behavioral outcomes of a 2-year teacher professional-development program for publicly funded prekindergarten and kindergarten in Chile. This cluster-randomized trial included 64 schools (child N = 1,876). The program incorporated workshops and in-classroom coaching. We found moderate to large positive impacts on observed emotional and instructional support as well as classroom organization in prekindergarten classrooms after 1 year of the program. After 2 years of the program, moderate positive impacts were observed on emotional support and classroom organization. No significant program impacts on child outcomes were detected at posttest (1 marginal effect, an increase in a composite of self-regulation and low problem behaviors, was observed). Professional development for preschool teachers in Chile can improve classroom quality. More intensive curricular approaches are needed for these improvements to translate into effects on children.