This study combined two important frameworks--teacher self-regulation and pedagogical content knowledge (PCK)--to reveal whether they were related to each other. To fulfill this aim, researchers utilized a case-study design. Data were collected from five preservice chemistry teachers through semi-structured interviews, lesson plans in the form of content representations, and video recordings of teaching practice. Both deductive and inductive analyses were used to analyze the data. Results indicated that preservice teachers utilized different PCK components in each self-regulation phase. They were good at regulating their teaching when they had developed PCK components. Especially, a lack of subject matter knowledge accounted for ineffective self-regulation in teaching. The findings of this study imply that teacher education programs should provide meaningful opportunities to preservice teachers for improving both their self-regulation for teaching and PCK.