Introduction: Gender stereotypes in schools influence how students perceive their academic and vocational abilities. Teachers play a crucial role in the transfer and transformation of these stereotypes. Teacher training must address these biases to promote equitable education. This research aims to design and validate a scale to identify how gender stereotypes have been internalized in teachers, identifying areas of intervention that promote gender equality in the educational environment. Method: This study, instrumental in nature with a descriptive and cross-sectional design, developed and validated a psychometric instrument to measure gender stereotypes in adults. The psychometric properties, validity, and reliability of the instrument were evaluated in a sample of 722 teachers from Antioquia, Colombia. Data analysis included expert review, exploratory and confirmatory factor analysis, and structural equation modeling, ensuring the reliability and validity of the final instrument. Results: The Gender Stereotype Internalization Scale for adults, validated for teachers, has a solid factorial structure of 17 items and four dimensions, supported by exploratory factor analysis, confirmatory factor analysis, and SEM, with a total variance of 58%, high internal consistency, confirmed convergent and discriminant validity, with appropriate CR and AVE indices, and HTMT values below 0.85. The SEM model fit indices (RMSEA=0.023, SRMR=0.038, CFI=0.997, TLI=0.996) showed excellent fit and significant relationships between some dimensions. Discussion or Conclusion: The high internal consistency and reliability of the scale demonstrate its suitability for assessing the internalization of gender stereotypes in this population. It provides a useful tool for evaluating gender stereotypes in teachers, facilitating the identification of biases and the implementation of training programs that promote equity in schools. This study contributes to understanding and reducing gender inequities in the educational field.