Trust is an important factor in improving the performance of the healthcare system. This study aimed to develop a validated scale to measure trust in the public healthcare system. We adopted a sequential exploratory mixed study design, with developmental and testing phases. In the developmental phase, the construct of "healthcare system trust" was conceptualised and items were generated on the basis of information from a review of the literature on trust, in-depth interviews and a review of other scales. Exploratory factor analysis was employed for item reduction. In the testing phase, the reliability and validity measures were established. The face validity, content validity and construct validity of the scale were assessed. The final scale was a Likert-type scale with 23 items, 16 of which measured trust in the healthcare providers and 7, in healthcare institutions. The scale is a valid and reliable tool for measuring trust in the public healthcare system.