Longitudinal data of psychotherapy theoretical orientations (PTO) for faculty from within clinical psychology programs were analyzed for a period of over two decades. Results from multilevel modeling demonstrated that clinical psychology has moved from a field that was relatively balanced in percentages of faculty from cognitive-behavioral (CBT), psychodynamic, humanistic, behavioral, and family PTOs to one that has shown highly significant linear growth for a single PTO: CBT. All other PTOs (except family) showed significant linear decline. To some extent, important research findings from other PTOs have been co-opted into CBT, but essential aspects of this work have been stripped down, muddied, or lost in a conflation with CBT treatments. We suggest that the field has lost significant intellectual diversity during the past two decades and identify how intellectual monocultures have been damaging to the success of other scientific disciplines and research groups. Tangible solutions are offered to correct this trend, including the establishment of an intellectual diversity task force, the APA's dissuasion of the establishment of monocultures within its evaluation of training, increased support for research investigation of more diverse approaches to psychotherapy, organizing of minority PTOs in order to lobby for larger research and professional training goals, and increased mentoring opportunities from minority PTO faculty.