For this review, the authors synthesized quantitative and qualitative research on collaborative learning to examine the relationship between teacher guidance strategies and the processes and outcomes of collaboration among students (66 studies). The results show that several aspects of teacher guidance are positively related to student collaboration, for example when teachers focus their attention on students’ problem solving strategies. During student collaboration, opportunities arise for students to engage in collaborative activities that support their learning process. The way teachers take more or less control of these moments determines whether these opportunities can be turned into real moments of learning for the students. This review highlights the important yet challenging role of the teacher during collaborative learning.