Mobile applications are popular among young children, yet there is a dearth of studies examining their impact on learning and development. A systematic review identified 19 studies reporting learning effects on children 2 to 5 years old. The number of children participating in experimental, quasi-experimental, or mixed-method studies was 862 and in descriptive or correlation studies, 941. The majority of studies reported positive effects on literacy development, mathematics, science, problem-solving, and self-efficacy. Among the factors explaining observed effects were design features, the role of adults, and a similarity between applications and transfer context. Although drawing firm conclusions remains a challenge, this review forms a first step towards systematic research in the field and contributes to shaping directions for future research.