This meta-analysis examines the effects of Montessori Education (ME) on five dimensions of development and learning in preschool and school-age children. It includes data from 33 experimental or quasi-experimental studies comparing ME with other pedagogical approaches (268 effect sizes; n = 21,67). These studies were conducted in North-America, Asia and Europe, and published between 1991 and 2021. Effect size estimated using Hedges’ unbiased g, and a 3-level multilevel meta-analytic approach applied due to the dependency among the effect sizes obtained from the same study. Results showed that ME’s effects on development and learning are positive and vary from moderate to high, depending on the dimension considered: cognitive abilities (g = 0.17), social skills (g = 0.22), creativity (g = 0.25), motor skills (g = 0.27), and academic achievement (g = 1.10). Analyses of different moderators did not reveal differences by school level, type of publication and continent. (author abstract)