Introduction: This study aimed to standardize, stabilize, and validate the optimism questionnaire based on the theory of planned behavior in the first-grade high school male adolescents. Materials and Methods: The present descriptive study was conducted on 170 male students in the first grade of high school. The study data were collected using a questionnaire. In order to determine the reliability of the questionnaire, Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were performed using the SPSS statistical software (version 19) and SAS 9.2. Results: High internal consistency values were obtained for all the subscales. The results of factor analysis showed that 14 significant factors had eigen values greater than one values and 71.22% of the variance was determined by these factors. In addition, using CFA based on the theory of planned behavior, four factors were considered for the 45 questions of the questionnaire which determined 39.98% of the variance. Conclusion: The results indicated that the optimism questionnaire was a valid and reliable instrument to be used among the students in the first grade of high school.