The general chemistry laboratory is an appropriate place for learning chemistry well. It is also effective for stimulating higher-order thinking skills, including reflective thinking, a skill that is crucial for science teaching as well as learning. This study aims to examine the effects of feedback-supported reflective journal-keeping activities on first-year pre-service science teachers' achievement. The pre-service science teachers were observed for eight weeks by collecting their journals. At the beginning and end of this process, an achievement test was administered. At the end of the study, the participants were also interviewed. It was found that feedback-supported reflective journal-keeping activities improved the first-year pre-service science teachers' achievement scores, and the majority of the participants believed that the activities had positive effects on their meta-cognition and learning.