Novel and unpredictable learning environments are a feature of school-to-college transitions that erode students' academic control, emotional resilience, and achievement (Perry, Hall, & Ruthig, 2005). Although motivation interventions can benefit college students (Koenka, 2020), few studies have examined treatment efficacy for students of varying socioeconomic backgrounds. This randomized treatment-control study assessed whether a cognitive-reframing intervention (attributional retraining [AR]) improved cognitive, affective, and performance outcomes of students with debt in a two-semester, online course. For in-debt students, AR (vs. no-AR) fostered cognitive reframing of achievement setbacks to increase academic control, adaptive emotions, post-treatment performance, and final course grades. Changes in maladaptive causal attributions mediated AR-grades efficacy in a path sequence specified by Weiner's (1985, 2014, 2018) attribution theory. Findings advance motivation intervention research by showing AR boosts achievement for students with debt, mediated by theory-derived cognitive and affective processes.