Pediatric primary care (PPC) settings provide optimal contexts for pediatric psychologists to deliver behavioral health services, including health promotion, prevention, early identification, and intervention. Policy statements and recommendations detail mental health competencies for PPC and delineate competencies for primary care psychology, providing a roadmap for training and preparing pediatric psychologists to work in primary care settings. This article focuses on the developmental progression of professionalism in postdoctoral fellowship training in PPC psychology. Using the Professionalism Cluster of the training competencies in pediatric psychology (Palermo et al., 2014), we apply the competencies to fellowship activities and provide examples of behavioral anchors that demonstrate readiness for independent practice. Project CLIMB (Consultation Liaison In Mental Health and Behavior) is an integrated behavioral health services program embedded in an urban, pediatric residency teaching clinic located at a regional children’s hospital within a large university system. Postdoctoral fellows train in 1 of 2 tracks, general PPC or early childhood mental health in PPC. Fellows engage in clinical care, scholarly activities, training and education, and professional development efforts under the supervision of pediatric psychologists. Goal setting, continuous evaluation, and reflection facilitate fellows’ preparation for independent practice. The Project CLIMB fellowship model illustrates the potential of training within PPC settings to cultivate competent and skilled pediatric psychologists.