Objective: A qualitative study sought to understand the transition experiences of United States (U.S.) military Service members found “unfit for duty” following medical and physical evaluation boards (MEBs and PEBs). Methods: Confidential telephone interviews were conducted with 25 current and prior Service members. Participants were asked to share their experiences before, during, and after the MEB and PEB processes. To that end, interview questions were designed to gather the following types of transition experiences: (1) health conditions experienced during the medical disability evaluation process; (2) reactions to being recommended for separation, (3) transition-related stress and challenges, and (4) coping strategies. Salient themes were identified across chronological narratives. Results: Conditions that participants’ experienced included debilitating physical (e.g., injury) and/or mental health (e.g., post-traumatic stress disorder) conditions. In response to the “unfit for duty” notice, some participants reported emotional distress (e.g., anxiety, sadness, anger) connected to a sense of uncertainty about the future. Other participants reported relief connected to a sense of progression toward their medical disability claim status. Transition stress included the length of the MEB/PEB process, impact of the COVID-19 pandemic on the process, experiences of financial stress, impact on family life, and the compounded effect of these stressors on emotional distress, including depression and suicidal thoughts. Participants reported using adaptive (e.g., psychotherapy) and maladaptive (e.g., excessive drinking) strategies to cope with stress. Conclusions: The notable emotional distress and transition stress experienced by Service members found “unfit for duty” highlight the need for increased support and interventions to facilitate adaptive coping strategies during this vulnerable period.