Introduction: The provision of mental health care services requires the involvement of diverse groups of professionals. This presents both challenges and opportunities for their successful collaboration due to issues such as insufficient understanding of the concepts, values, and activities between professions or disciplines, thereby complicating everyday practical work. In this study, we aimed to examine differences in the beliefs of psychiatrists, psychologists, and theologists about the location of the mind, soul, and self; their attitudes towards dualism; the prevalence of implicit models (biological, behavioral, cognitive, psychodynamic, social constructivism, social realism, spiritualist, and nihilistic) for four mental disorders (schizophrenia, depression, generalized anxiety disorder, and antisocial personality disorder). We also sought to explore the relationship between their beliefs in the biological or spiritual model of the four disorders with their belief in monism or dualism. The relationship between these constructs could influence the understanding of the concept of mental health. Methods: We applied an anonymized online questionnaire to a sample of psychiatrists, psychologists, and theologists in Croatia between January 15, 2018, and June 15, 2018. After excluding incomplete responses, the final sample consisted of 312 participants: 122 psychiatrists, 116 psychologists, and 74 theologists. The study questionnaire had three sections. In the first section, participants were shown a drawing of the human body with numbers indicating eight different regions and were then queried to show which one best represents the location of the self, soul, and mind. The second section contained the Dualism Scale, which measured different beliefs about dualism/monism and thus assessed the degree of agreement with the belief that the mind and brain are separate entities. The third part included the Maudsley Attitude Questionnaire (MAQ), which investigated participants' preferences for implicit models of mental disorders. Validation analyses have shown that all three questionnaires have sufficient reliability and factor structures. Results: We saw significant differences (p < 0.001) in how the psychiatrists, psychologists, and theologists located the soul, while all three groups agreed on the location of the mind. Compared to psychiatrists, theologists were five times more likely (odds ratio (OR) = 5.38, correlation coefficient (β) = 0.140, p < 0.001) to prefer dualism, while psychologists were twice as likely (OR = 2.27, β = 0.046, p = 0.023) to prefer monism. Psychiatrists supported the biological and psychodynamic models more than the other two groups for all four disorders; psychologists preferred the cognitive model; while theologians consistently preferred the spiritual model for all disorders. A higher degree of belief in dualism was related to a significantly increased tendency towards the spiritual model (R2 = 0.34) of mental disorders, while a higher degree of belief in monism was related to a significantly increased tendency towards the biological model of mental disorders (R2 = 0.15). Conclusions: Our findings on the models of mental disorders, dualism, monism, and the location of the soul, mind, and self raise significant questions and provide insight into different perspectives that shape our understanding of mental health and consciousness. This has implications for theoretical research, clinical practice, and interdisciplinary dialogue and may lead to new approaches and methods in the study of mental phenomena, thereby contributing to the development of a more comprehensive approach to the care of individuals with mental health challenges.