This study examined the effect of diaries on self-regulation strategies of the pre-service science teachers. The participants of the study were 60 pre-service science teachers, 30 of which were in the experimental and the remaining 30 were in the control group. The Pintrich's self-regulation model was taken as a basis in the study. The Pintrich's model of self-regulation includes 3 general categories of strategies: (a) cognitive learning strategies, (b) metacognitive or self-regulatory strategies to control cognition, and (c) resource management strategies. In the study, the pre-service science teachers in the experimental group reported the self-regulation strategies they used for daily learning activities by writing the diary-report form for fourteen weeks. The data of the study were collected by the motivated strategies for learning questionnaire. At the end of the study, the intrinsic motivation, task value, metacognition, time management strategy usage status of the experimental group which reported their self-regulation strategies were significantly different from those of the control group. (Contains 2 tables.)