Objective: To assess the relationship between rehabilitation needs and mental health symptoms in Veterans and Service Members with polytrauma, including history of mild traumatic brain injury (TBI). Setting: Five Veterans Affairs (VA) Intensive Evaluation and Treatment Programs. Participants: Veterans and Service Members enrolled in the VA TBI Model Systems study who completed a follow-up greater than 6 months postprogram. Design: Cohort study. Main Measures: Primary regression analyses included rehabilitation needs (Rehabilitation Needs Survey) and post-traumatic stress symptoms (PTSD Checklist-Civilian version). Age, sex, months from rehabilitation to follow-up interview, preinjury mental health, disability level (Glasgow Outcome Scale–Extended), and number of comorbidities were included as covariates. Secondary analyses applied the same model structure to assess the relationship between rehabilitation needs and anxiety (Generalized Anxiety Disorder-7) and depression (Patient Health Questionnaire-9) symptoms. Results: Most Veterans and Service Members with polytrauma, including mild TBI, reported a current need for services to control physical symptoms (55%) and greater than one-third endorsed a current need for services to improve memory (46%), manage emotions (45%), improve health (44%), manage daily stress (42%), and solve daily problems (38%). Adjusted regression analyses revealed that rehabilitation needs were significantly and positively associated with post-traumatic stress, anxiety, and depression self-report symptoms. These relationships were maintained when analyses were repeated with mental health–related items removed from the Rehabilitation Needs Survey, suggesting the finding was not solely because of mental health needs. Higher comorbidity burden and disability were also independently associated with higher rehabilitation needs. Conclusions: Veterans and Service Members with polytrauma, especially those with elevated post-traumatic stress, anxiety, and/or depressive symptoms in the context of mild TBI, could benefit from ongoing access to evidence-based psychotherapies and other specialty care, rehabilitation, and support services to manage long-term care and rehabilitation needs in the chronic phase of injury.