Citizen Science is an ever-growing field of public engagement with science, and recent years have seen an increasing number of studies examining its potential. This study reviews this research to determine the educational and scientific outcomes of Citizen Science. A literature search produced 1,240 articles that were subsequently coded according to their main focus. Articles fell into one of three main categories: (a) empirical scientific articles, (b) narrative project descriptions, and (c) theoretical and technical conceptualizations. Hundred and forty-eight studies investigated educational outcomes of participation in Citizen Science such as effects on interest in science or motivation. These studies were examined further to assess the achievement of educational outcomes of Citizen Science. In terms of changing epistemological beliefs, for example, Citizen Science seems to have little effect. Overall, there is currently a lack of empirical studies to assess the educational outcomes comprehensively. In contrast, many empirical scientific articles answered research questions in different scientific disciplines based on Citizen Science data and many studies confirmed a high level of Citizen Science data quality providing information on the scientific outcomes. Implications for future research on Citizen Science are discussed.