The main goal of this study was to test whether feedback from a lecturer and tutor on an initial reflective journal entry fosters reflection quality in a subsequent journal entry and reflection skills in student teachers. To address these questions, we, a team of educators and psychologists, conducted a field experiment during the practical semester. Student teachers (N = 54; 40 female) wrote two reflective journals about their own classroom teachings on an online-platform and were randomly assigned to one of two conditions: (a) reflective journaling with feedback (experimental condition, n = 27) or (b) reflective journaling without feedback (control condition, n = 27). Feedback in reflective journaling fostered reflection quality in the subsequent journal entry and conceptual knowledge about reflection. These findings indicate that feedback in reflective journal-keeping exerts a powerful influence in fostering reflection in student teachers during their practical semester.