The current study examined how teachers' perfectionism (personal standards [PS] and concern over mistakes [COM]) relates to their achievement goals for teaching, instructional practices (creation of mastery vs. performance classroom goal structures), job satisfaction, and flow experience during teaching. The data were collected from teachers (N = 143; mean age = 43.5; 70% female; 100% European American) practicing in the Midwestern U.S. Path analyses indicated that teachers' high personal standards predicted endorsement of mastery goals for teaching, creation of mastery goal structure emphasizing personal progress and learning, high job satisfaction, and frequent flow experience during teaching. On the contrary, teachers' high concern over mistakes predicted endorsement of performance-approach and -avoidance goals, creation of classroom performance goal structure emphasizing competition among students, low job satisfaction, and infrequent flow experience during teaching. A significant interaction between PS and COM was found for fluency (subscale of flow) experience, indicating that PS can buffer the harmful effects of COM. Therefore, the study evidenced the benefits of PS and the drawbacks of COM.