Context: Despite their widespread use in medical school selection, there remains a lack of clarity on exactly what situational judgement tests (SJTs) measure. Objectives: We aimed to develop an SJT that measures integrity by combining critical incident interviews (inductive approach) with an innovative deductive approach. The deductive approach guided the development of the SJT according to two established theoretical models, of which one was positively related to integrity (honesty–humility [HH]) and one was negatively related to integrity (cognitive distortions [CD]). The Integrity SJT covered desirable (HH-based) and undesirable (CD-based) response options. We examined the convergent and discriminant validity of the Integrity SJT and compared the validity of the HH-based and CD-based subscores. Methods: The Integrity SJT was administered to 402 prospective applicants at a Dutch medical school. The Integrity SJT consisted of 57 scenarios, each followed by four response options, of which two represented HH facets and two represented CD categories. Three SJT scores were computed, including a total, an HH-based and a CD-based score. The validity of these scores was examined according to their relationships with external integrity-related measures (convergent validity) and self-efficacy (discriminant validity). Results: The three SJT scores correlated significantly with all integrity-related measures and not with self-efficacy, indicating convergent and discriminant validity. In addition, the CD-based SJT score correlated significantly more strongly than the HH-based SJT score with two of the four integrity-related measures. Conclusions: An SJT that assesses the ability to correctly recognise CD-based response options as inappropriate (i.e. what one should not do) seems to have stronger convergent validity than an SJT that assesses the ability to correctly recognise HH-based response options as appropriate (i.e. what one should do). This finding might be explained by the larger consensus on what is considered inappropriate than on what is considered appropriate in a challenging situation. It may be promising to focus an SJT on the ability to recognise what one should not do.