BACKGROUND: Medical ethics is a significant learning topic for medical students, and often studied through small group learning (SGL) to encourage critical thinking (CT) and tolerance for ambiguity, both considered particularly important when coping with medical ethics dilemmas. However, a previous study about CT and tolerance for ambiguity in medical ethics SGL produced mixed results. Debating is a pedagogical tool known to enhance CT but never used before in medical ethics learning. This paper examines whether the use of debate may enhance medical ethics SGL by contributing to the CT of students and their tolerance of ambiguity. METHODS: Intervention study using the qualitative microanalysis research method, based on videotaped observations that were analyzed through Kamin's model of CT and non-CT. The study was conducted at Bar-Ilan University's Faculty of Medicine in the years 2017-2019. Forty-four students and 4 facilitators participated, equally split between 4 small groups. Twenty-four medical ethics SGL sessions at the beginning and end of the year were videotaped, 2 groups - with no intervention, 1 group included partial debate intervention and 1 group fully used debates. Results were compared for changes in CT and ambiguity before and during the intervention period. RESULTS: The full intervention (debating) group had the highest increase in utterances reflecting CT, thus actually doubling the median number of CT utterances at the end of the year in comparison to the median number at the beginning of the year. In a similar manner, the debate group exhibited the only group in which there was an increase in the median utterances of tolerance to ambiguity. Nevertheless, the debate group also exhibited the largest increase in the median non-CT utterances and the lowest decrease of intolerance to ambiguity, when comparing the end of the year to the beginning of the year sessions. CONCLUSIONS: Debating is an important enhancement to SGL in medical ethics; however, it does not guarantee a complete absence of non-CT.