Portfolios are credited with an array of potentials (e.g. to reinforce student teachers' professionalisation). Their use in teacher education has rapidly increased in recent years, particularly because of system-wide implementations. Nevertheless, studies on portfolios have not followed this growth. A systematic review of studies is pending. Hence, this study systematically examines the available portfolio research literature (N = 246 texts), focusing on joint research topics and analyses quantitative empirical effects (e.g. on student teachers' reflexivity) in more depth using vote-counting. Overall, there are many findings on student teachers' perceptions of portfolios, but only a few examine portfolios' quantitative empirical effects. Findings indicate that working with portfolios is likely to increase the level of student teachers' reflective writing. Even though the analysed research provides initial insights into portfolios, their significance (e.g. effects on developing professional knowledge) remains unclear.