The gender and ethnicity gap in academic achievement constitutes one of today’s key social problems. The current study, therefore, assessed the effects of a brief, evidence-based online intervention aimed at enhancing goal-directed conceptualization and action among first year college students (N =703) at a large European business school. The academic performance of these students was contrasted with that of three pre-intervention control cohorts (N =896, 825 and 720), with particular attention paid to the role of gender and ethnicity. The intervention boosted academic achievement and increased retention rates, particularly for ethnic minority and male students (who had underperformed in previous years). The gap in performance between men and women, and for ethnic minorities versus nationals, became considerably smaller within the intervention cohort. After Year 1, the gender gap closed by 98%, and the ethnicity gap by 38% (rising to 93% after the second year). All groups in the intervention cohort performed significantly better than control cohorts, but the effect was particularly large for males and ethnic minorities. The increase in performance was largest for ethnic minority males: they earned 44% more credits, and their retention rate increased 54%. Overall, the results indicate that a comprehensive goal-setting intervention implemented early in students’ academic careers can significantly and substantially reduce gender and ethnic minority inequalities in achievement.