It is clear that adequate academic and continuing education/training for correctional mental health professionals is imperative if their practice is to be effective. To help shape such training, the clinical and correctional knowledge ranked most meaningful and relevant by psychologists practicing in federal prisons is determined. Overall, results suggest nine core bodies of knowledge representing a mix of clinical (e.g., psychopathology, suicide prevention, psychopharmacology) and prison-based domains (e.g., interdepartmental communications, safety, confrontation avoidance) form the heart of their work. In terms of where such knowledge was obtained, graduate school is frequently endorsed for the more clinical domains, but the correctional domains are transmitted namely through on-the-job training. Recommendations for training psychologists to practice in corrections include the development of a two-tiered training strategy that offers a curriculum in basic psychological knowledge unique to corrections and an advanced curriculum that builds on foundational clinical knowledge obtained in graduate school.