The author sought to determine whether self-evaluation instruction had an impact on student self-evaluation, music performance, and self-evaluation accuracy of music performance among middle school instrumentalists. Participants (N = 211) were students at a private middle school located in a metropolitan area of a mid-Atlantic state. Students in intact classes, grades 5 through 8, were assigned to one of three treatment groups: self-evaluation instruction (SE-I), self-evaluation only (SE-O), or no self-evaluation (SE-No) for treatment lasting 5 weeks. All groups played through music used in the study at each lesson and heard a model recording of it. Participants in the SE-I group received instruction in self-evaluation while students in the SE-O group self-evaluated their performances daily and the SE-No group received no additional instruction. Results suggest that instruction in self-evaluation had little impact on students' self-evaluation accuracy or music performance, although grade level did influence music performance. Additional time may be necessary for students to learn to evaluate their own performances effectively; however, it is interesting that students' music performance did not appear to suffer from time spent in self-evaluation instruction or practice. Music teachers may wish to consider implementing self-evaluation strategies to help students develop the skills necessary for successful self-regulation of music performance. (Contains 4 tables.)