Introduction: Low back pain is a symptom with biopsychosocial implications with the potential to reach the whole individual. The school-age coincides with an important period in human development and in which inequalities and compensation resulting from poor posture or structural changes may increase the chance of the emergence of pain. Objective: To estimate the prevalence of low back pain among adolescents. Methods: The sample consisted of 166 adolescents between 11 and 18 years of age (86 girls and 80 boys) enrolled in a private school in a town in the state of Piauí, in the academic year 2012. A structured questionnaire with closed questions on gender and low back pain aspects was used. Results: Almost 80% of the students reported the presence of low back pain in the past year, and nearly half (41.3%) reported pain classified as 3, according to faces pain scale. About two-thirds of the adolescents (63.1%) said they did not fail to perform their daily activities due to pain.There was no statistically significant association between gender and low back pain (p = 0.117) or pain intensity (p = 0.065), although for the latter a variable marginal p-value was found. Conclusion: A high prevalence of low back pain was found in the study group without gender differences regarding pain characteristics.