Background: The concern and analysis about the knowledge possessed by teachers of basic general education persists in academic debate and professional practice. It is noteworthy that in the studies consulted, there is no precise evidence that determines with accuracy the configurations of these knowledge factors that function as the basis of the teaching profession. Therefore, the objective of this study is to establish the construct validity and reliability of the questionnaire on the nature or origin of the academic knowledge of teachers of basic general education, adapted from the Pedagogical Content Knowledge (PCK) Competence Model. Methods: A methodological study was established that applies a test to the processes of reliability and internal consistency. The construct validity was performed through (n = 8) expert judges, using Cohen's Kappa. An exploratory factor analysis was performed following the criteria of the Kaiser-Meyer-Olkin Coefficient (KMO), the Bartlett sphericity test and the principal components extraction method in the factor analysis with varimax rotation. The sample consisted of (n = 27) teachers of basic general education of the Ibarra Canton. Results: The results show a reliability analysis for the instrument obtained a Cronbach’s alpha (α = 0.901), estimated to be an excellent level. Conclusions: The questionnaire is relevant, valid and reliable, adapting to the needs of teachers of basic general education to determine the nature or origin of the academic knowledge in a fast and reliable manner.