Psychology internship and fellowship years are exciting yet challenging times of professional development, as geropsychologists-in-training transition to independent practice and work to consolidate their identities as professional geropsychologists. Geropsychology supervisors help interns and fellows to develop and refine attitude, knowledge, and skill competencies for geropsychology practice. Transformational geropsychology supervisors also serve as mentors. They offer professional role modeling, acknowledgement of unique strengths and areas for growth, socialization to the geropsychology community, and communication of confidence and support for the professional development of interns and fellows.The internship and fellowship years are intense periods of professional development for clinical and counseling psychologistsin-training, including those who choose to focus training in the field This article not subject to US copyright law. The authors thank their Geropsychology colleagues, supervisees, and peers who have shared perspectives on supervision and mentoring over the years. In particular, Michele Karel thanks her colleague Jennifer Moye and previous Fellows, now colleagues, Kelly Trevino and Michelle Braun for their collaboration and support in geropsychology training. Further, Michele Karel thanks those geropsychology interns and fellows who responded to an e-mail inquiry and shared their thoughts about supervision and mentoring during their geropsychology internship and=or fellowship years at Veterans Health Administration (VA) Boston. Carolyn Stead thanks the many excellent supervisors who provided her with invaluable mentorship and support during internship and fellowship years. This material is the result of work supported with resources from and the use of facilities at the Boston VA Medical Center.