This study examined pathways through which family socioeconomic status may influence adolescents' academic achievement. We focused on parental monitoring and adolescents' after-school time-use patterns as linking mechanisms. Participants were 441 twelve- to fourteen-year-old Korean adolescents who participated in the Korea Welfare Panel Study. Higher family economic pressure was linked with lower parental monitoring through elevated levels of parental depression. Parental monitoring was associated with more time spent in structured learning-oriented activities and less time spent in unstructured nonacademic activities. Both types of time-use activities and parental monitoring were associated with academic achievement. The results supported both the "family stress model" and the "family investment model," indicating that families' socioeconomic conditions were directly and indirectly linked to adolescents' academic achievement. The findings are discussed in the context of Korean culture, which emphasizes high parental involvement and economic investment in children's education. We also present broader implications beyond the local context.