The purpose of this study was to develop the Korean School Engagement Scale for Middle School Students (K-SES:M) and to test its reliability and validity. Free-response questionnaire surveys and focus group interviews, which were conducted to overcome the construct bias resulting from the use of translated scales, yielded 90 pilot items. These items were administered to 1,036 middle school students in Grades 7 to 9 and the data were analyzed through exploratory factor analyses, confirmatory factor analyses, correlational analyses, and concurrent validity analyses. The Korean School Engagement Scale for Middle School Students consisted of 48 items, which were divided into 8 subscales (i.e., satisfaction with school life, valuing of schoolwork, rule compliance, extracurricular activities, peer relations, student-teacher relations, attentiveness during instructional activities, self-regulated learning). Internal consistency reliabilities of the subscales were high, and positive correlations among the subscales were statistically significant. The eight subscales of the Korean School Engagement Scale for Middle School Students were positively correlated with the subscales of the School Engagement Measure and the Korean Academic Engagement Inventory. The results from confirmatory factor analyses indicated that the fit of the first-order eight-factor model was better than the second-order four-factor model and the second-order one-factor model. Furthermore, the evidence suggests that the Korean School Engagement Scale for Middle School Students may be a reliable and valid measure and may be useful for understanding and assessing various aspects of middle school students’ engagement with school. Limitations of this study and suggestions for future research were discussed.