Many experimental studies have reported the effects of strategy instruction (SI) on reading comprehension in Korea, but the reported results are not conclusive. This metaanalysis study, therefore, aims to provide reliable common effects of SI on Korean learners’ reading comprehension. The study also aims to investigate how context (institution, L2 proficiency, gender) and treatment variables (strategy type, numbers of different strategies used, test types) affect the effectiveness of SI on the reading comprehension ability of Korean L2 learners. Through a comprehensive search, 37 primary studies were selected and 45 samples were coded into CMA software to calculate effect sizes by computing Heges’ g. The results of this meta-analysis showed a moderate effect of SI on reading comprehension (ES=.58). All moderating variables except L2 proficiency and gender had a statistically significant moderating effect with medium to large effect sizes for 7 variables and small effect sizes for 4 variables. Findings and pedagogical and research implications are discussed.