Promoting students' critical thinking skills is an important task of higher education. Colleges and universities have designed various instructional interventions to enhance students' critical thinking skills. Empirical studies have yielded inconsistent results in terms of the effects of such interventions. This meta-analysis presents a synthesis of empirical studies designed to promote measurable changes in students' critical thinking skills using instructional interventions. Findings demonstrated statistically significant but small average effect size and evidence of heterogeneity among studies. Hierarchical linear model was adopted to explore potential predictors of the variance across effect sizes. Results showed that student discipline and treatment length explained part of the variability among treatment effects. Limitations and implications are discussed. (Contains 3 tables and 1 figure.)