To validate a Spanish-language questionnaire on adolescent eating behavior based on Social Cognitive Theory. The validity (reliability and construct validity) of a self-administered questionnaire containing 28 questions with Likert scale-type response options was evaluated. School located in Tonala, Jalisco, Mexico (a peri-urban area) with approximately 1,400 students enrolled. One hundred fifty-two adolescents enrolled in the second year of a middle school in Tonalá, Jalisco, Mexico (mean age, 13.7 years; SD, 0.5 years; 64% female). The retest was completed by 70 adolescents chosen at random. The questionnaire's reliability was measured through internal consistency (Cronbach α) and reproducibility (intraclass correlation coefficient [ICC]). Construct validity was assessed using exploratory factor analysis. Five questions were eliminated from the questionnaire because of a lack of temporal stability (ICC ≤0.4). The exploratory factor analysis was satisfactory for 3 factors (41.89% of variance): environmental facilitators and social support, self-efficacy and self-regulation, and outcome expectations and outcome expectations value. The questionnaire had good internal consistency (α = 0.824) and excellent temporal stability (ICC = 0.849). The results substantiate the reliability and construct validity of this questionnaire. The questionnaire has the potential to use the assessment of Social Cognitive Theory constructs in clinical practice or in nutrition interventions aimed at modifying the eating habits of Spanish-speaking adolescents. Copyright © 2020 Society for Nutrition Education and Behavior. Published by Elsevier Inc. All rights reserved.