Continuing the transition to competency-based education, Hospice and Palliative Medicine (HPM) fellowship programs began using context-free reporting milestones (RMs) for internal medicine subspecialties in 2014 but quickly recognized that they did not reflect the nuanced practice of the field. This article describes the development of 20 subspecialty-specific RMs through consensus group process and vetting by HPM educators. A workgroup of content experts used an iterative consensus building process between December 2017 and February 2019 to draft new RMs and create a supplemental guide that outlines the intent of each RM, examples of each developmental trajectory, assessment methods, and resources to guide educators. Program directors, program coordinators, and designated institutional officers were contacted directly to solicit feedback. Most respondents agreed or strongly agreed that each RM represented a realistic progression of knowledge, skills, and behaviors, and that the set of milestones adequately discriminated between meaningful levels of competency. Similarly, respondents felt that the supplemental guide was a useful resource. The result is a set of carefully developed and broadly vetted RMs that represent a progression of development for HPM physicians during one year of clinical fellowship training.