Background: The existing literature supports the application of the principles of andragogy on patient education. But there is a lack of a suitable tool for assessing patient education's conformity with these principles. Purpose: This study was conducted to develop and evaluate the psychometric properties of a questionnaire that measures the degree to which the patient education adheres to the principles of andragogy. Methods: The primary instrument, consisting of 70 items, was developed after the literature review. The psychometric properties of the instrument were determined. The content validity of the items was assessed by an expert panel review. Exploratory and confirmatory factor analysis was performed to test the construct validity. Cronbach's alpha coefficient was used to assess the internal consistency of the scale. A sample of 300 hospitalized adult CVD patients with a mean age of 54.93 ± 13.59 in 2 heart hospitals, were selected through convenience sampling method. The data were analyzed using SPSS 16 statistical software. Results: After determining face and content validity, the questionnaire items decreased to 59. The exploratory factor analysis indicated the existence of 6 factors that accounted for 53.37% variance of the questionnaire. The confirmatory factor analysis revealed a good fit to a predetermined send of constructs. Analyses also indicated acceptable results for the internal consistency with Cronbach's alpha value (0.72 to 0.93). The final questionnaire was approved; this comprised of six factors with 40 items. Discussion: The psychometric evaluation of the APEQ resulted to a reliable and valid instrument. Translation to Health Education Practice: This instrument is helpful in assessing the adherence of patient education to the principles of andragogy, eliminating deficiencies and promoting the performance of health education providers in patient education.