It has been often hypothesized that environmental Citizen Science (CS) initiatives may contribute to the transformation of citizens into environmentally aware citizens. However, the potential of CS to support Education for Environmental Citizenship (EEC) has not been explored yet. A Systematic Literature Review (SLR), aligned with the PRISMA methodology, was conducted to examine how citizens’ participation in environmental CS initiatives contributes to the EEC, as a means by which citizens are empowered to apply actions in different scales to achieve environmental citizenship. A content analysis procedure was implemented on thirty-one empirical studies (n=31) covering the last two decades (2000-2020). The findings indicated that the majority of the reviewed environmental CS initiatives primarily enhanced citizens’ skills and knowledge over attitudes, values and behaviors; strengthened their personal and responsible environmental actions, on the private sphere and the local scale, and contributed to environmental outcomes that were mainly related to the solution and prevention of environmental problems. Finally, significant strong correlations were revealed between the EC competences, EC actions and EEC outcomes, according to the performed correlational statistical analysis.