Abstract: | Extracurricular involvement in the school‐age years has widespread potential benefits for children's subsequent socioemotional development, especially for low‐income youth. However, there is a dearth of research on interventions aimed at increasing school‐age extracurricular involvement in low‐income youth. Thus, the present study aimed to test the collateral effect of a brief, family‐focused intervention for low‐income families, the Family Check‐Up, on children's school‐age extracurricular involvement via improvements in maternal positive behavior support (PBS) in early childhood. The sample (n = 630, 50% female, 50% White, 28% Black/African American) represented a subsample of families from the Early Steps Multisite Study. At the age of two, families were randomly assigned to the Family Check‐Up or Women, Infants, and Children Nutritional Supplement Services as usual. Mother‐child dyads participated in observed interaction tasks at child ages 2 and 3 that were subsequently coded to assess PBS. Primary caregivers reported on children's school‐age extracurricular involvement at ages 7.5, 8.5, and 9.5. Results indicated that although there was not a direct path between intervention status and children's school‐age extracurricular involvement, a significant indirect path emerged from intervention group to changes in PBS between ages 2 to 3 to children's school‐age extracurricular involvement. The results are discussed in terms of implications for designing preventive interventions in early childhood that promote extracurricular involvement at school‐age, particularly for children at risk for maladaptive outcomes. |