The scientific study of school engagement has recently been the subject of considerable interest in the field of educational psychology, and significant advances have been made in our knowledge of this construct. For instance, there is currently consensus in the scientific community that it is multifaceted, and has three dimensions: behavioral engagement, emotional engagement, and cognitive engagement. However, more advanced statistical analyses are needed to validate Spanish-language measures of school engagement, which this study proposes to do. The sample was comprised of 1,250 adolescents from Basque Country (49% boys, 51% girls) aged 12 to 15 years old (M = 13.72, SD = 1.09). The results of confirmatory factor analysis on the School Engagement Measure (Fredricks, Blumenfeld, Friedel, & Paris, 2005) supported a three-dimensional structure of school engagement (χ2(100) = 676.93, p < .001; GFI = .931; CFI = .906; IFI = .907; SRMR = .058; RMSEA = .068). Reliability indexes were satisfactory, ranging from .83 to .94. Adequate evidence of concurrent validity was found for the variable perceived school performance (p < .01). The results are discussed from an educational perspective, and with an eye to future research.