Meta-analyses have shown the positive effects of strategy instruction on student performance; however, little meta-analytical research has been conducted on its long-term effects. We examined the long-term effects of 48 metacognitive strategy instruction interventions on student academic performance. The results show a very small increase of the effect at long-term compared with the posttest effects. The instruction effect at posttest increased from Hedges’ g = 0.50 to 0.63 at follow-up test. Moderator analyses showed that low SES students benefited the most at long-term. Furthermore, instructions including the cognitive strategy ‘rehearsal’ had lower long-term effects compared to interventions without this component. Other specific strategies (within categories metacognitive, cognitive, management, or motivational) did not moderate the overall positive long-term effect of metacognitive strategy instructions. Particular attributes of the intervention –subject domain, measurement instrument, duration, time between posttest and follow-up test, and cooperation – neither had an impact on the follow-up effect.