To investigate the pedagogical effectiveness of oral corrective feedback (CF) on target language development, we conducted a meta-analysis that focused exclusively on 15 classroom-based studies (N = 827). The analysis was designed to investigate whether CF was effective in classroom settings and, if so, whether its effectiveness varied according to (a) types of CF, (b) types and timing of outcome measures, (c) instructional setting (second vs. foreign language classroom), (d) treatment length, and (e) learners' age. Results revealed that CF had significant and durable effects on target language development. The effects were larger for prompts than recasts and most apparent in measures that elicit free constructed responses. Whereas instructional setting was not identified as a contributing factor to CF effectiveness, effects of long treatments were larger than those of short-to-medium treatments but not distinguishable from those of brief treatments. A simple regression analysis revealed effects for age, with younger learners benefiting from CF more than older learners.