Introduction: Healthcare professionals face numerous stress-inducing daily stimuli, which can negatively impact their well-being, individual performance, and the dynamics of hospital teams. Studies have shown that self-knowledge is a mental health tool that benefits quality of life and stress. However, there are still no studies on healthcare professionals in hospital services. Thus, the present study aims to understand the effect of self-knowledge training, based on the Enneagram, on the well-being of healthcare professionals and hospital teams. Methods: This is a controlled longitudinal exploratory study with intervention. With a sample of 24 health professionals from Coimbra’s University Hospital Center (CHUC), 12 constituted the intervention group, which was given a self-knowledge course based on the Enneagram of Personalities, and 12 formed the control group. Both groups answered an online questionnaire before and after the intervention, consisting of seven scales – Perceived Quality of Life (EQ-VAS), Job-related Affective Well-being (JAWS), Self-Reflection and Insight (SRIS), Self-Awareness (SAOQ), Perceived Stress (PSS-10), Rumination and Reflection (RRQ), and Psychological Flexibility (Psy-Flex). The data obtained were analyzed descriptively and inferentially with the parametric Student’s t-test. The contents of the six open questions were subjected to a qualitative analysis. Results: The qualitative assessment revealed individual, interpersonal, and professional gains, with significant improvements in self-awareness, self-reflection, and insight, as well as enhanced relationships, empathy, and compassion. It also introduced new dimensions to the study, specifically teamwork, relationship improvement, empathy, difficulty with change, and difficulty in self-understanding. In the quantitative assessment, the intervention group started with lower proactivity (p=0.033) and a greater need for self-reflection (p=0.03), maintaining the latter after the intervention (p=0.023). By the end, the control group showed decreased acceptance (p=0.01) and, compared to the intervention group, showed a higher insight (p=0.01). Discussion: Despite the limitations of the study sample, particularly the small size and high heterogeneity, the intervention did not lead to any worsening but rather an improvement in the well-being of healthcare professionals, as demonstrated in the qualitative analysis. Considering the high burnout levels in the intervention group, the self-knowledge training appeared to play an essential role in maintaining the participants’ well-being. A long-term qualitative reassessment is suggested for further investigation. Conclusion: It was concluded that training in self-knowledge can be an effective tool in stress prevention and well-being preservation of hospital healthcare professionals with high levels of exhaustion.