The prevalence of back pain (BP) among children and adolescents has been increasing in the last years. Some authors advocate to promote the back health education in the school setting. It should be important to adopt a uniform suite of assessment instruments to measure the various constructs. The present study aimed to translate and validate a Spanish-language adaptation of the Back Pain and Body Posture Evaluation Instrument (BackPEI) for adolescents. The translation and cross-cultural adaptation were performed according to the recommendations of guidelines. Reliability was tested by applying the questionnaire to 224 secondary students, at two different times with a 7-day interval. In general, the Spanish version presented adequate agreement for questions 1–20. The question about the pain intensity did not show differences between the averages for the test (X= 4.72 ± SD= 2.33) and re-test (X= 4.58 ± SD =2.37) (p = .333), and the responses for these two tests were highly correlated (ICC= .951, 95% IC: .928- .966; p= .0001). Psychometric testing indicated that the Spanish version of the BackPEI provided valid and reliable scores that were similar to the results obtained with the original Brazilian version.