Prior research has shown that social-emotional learning (SEL) interventions offer promise for supporting young children's outcomes, but implementation problems are frequent, especially in low-resource contexts. This study describes the adaptation and efficacy of a new, classroom-based SEL intervention for children aged 3 to 6 years in early childhood education programs in Brazil. SEL Kernels are simple, brief, targeted SEL activities that can be flexibly implemented by teachers. Research Findings: Results of a quasi-experimental study using teacher reports with 314 Brazilian children (164 male, 150 female) who did (n = 205) and did not (n = 109) receive SEL Kernels suggested intervention-related improvements in teachers' reports of child behavior problems (d = 0.65) and emotion regulation (d = 1.12) in this setting. Practice or Policy: Implications of this work -- including the importance of teacher buy-in and implementation -- are discussed.