Collusions, interpersonal phenomena with an impact on patients, significant others, clinicians, and care, are mainly described in the psychotherapeutic literature but also occur in the medical setting. Comprehended as an unconscious bond between two or more persons from a psychotherapeutic perspective, definitions and collusive situations described in the medical setting vary. The question arises whether medical collusions, compared to collusions occurring in the psychiatric setting emerge in different clinical situations or are not identified as transference-countertransference experiences, since there is less sensitivity for the unconscious dimensions of care. We systematically reviewed the medical literature on collusions. Even though a read threat, avoidance of unpleasant feelings (mainly anxiety), runs through the described collusions, the unconscious dimensions and associated defensive maneuvers are rarely evoked. Given the expressed desire to act on collusions in medicine, involving third-party psychiatric liaison clinicians, who supervise clinicians, and hereby help to disentangle collusions, could be beneficial.