Feasibility of Remote Tai Chi

Inclusion Criteria: * Veteran status as indicated by self-report * PTSD Case Definition. Veterans who meet Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) diagnostic criteria according to DSM-5 diagnostic algorithm for current PTSD as assessed on the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) will be eligible for the study. A diagnosis of current PTSD requires: a traumatic stressor (Criterion A) and the requisite number of symptoms at a severity level of 2 or higher in each symptom cluster. Each symptom is rated on a severity scale of 0 (no symptoms) to 4 (extreme), with 2 representing clinically significant and clearly present symptomatology. An individual must endorse at least one reexperiencing (Criterion B) symptom, at least one avoidance (Criterion C) symptom, at least two symptoms of negative alterations in cognition and mood (Criterion D), and at least two hyperarousal (Criterion E) symptoms. In addition, these symptoms must have been present for at least one month (Criterion F) and cause either clinically significant distress or functional impairment (Criterion G). * Chronic pain as indicated by complaints of musculoskeletal pain in one or more body regions for six months or more. * Willing to abstain from initiating evidence-based and mindfulness-based psychotherapy for PTSD, pain and related disorders until completion of the study (i.e., prolonged exposure, cognitive processing therapy, cognitive-behavioral treatment for insomnia or pain, acceptance and commitment therapy, dialectical behavior therapy, mindfulness-based stress reduction). Once enrolled, however, if other providers prescribe treatment or if participants require additional intervention (such as to manage a safety or substance abuse condition), treatment will be allowed, and appropriate referrals will be made. Individuals who are currently engaging in short-term (e.g., 12-week protocol) evidence-based treatment will not be eligible until treatment has ended. * Access to internet and home computer or tablet device that will allow telehealth delivery of intervention. * Available to attend either intervention group at the times they are scheduled. * Enrolled and eligible to receive care in Veterans Health Administration (VHA). The investigators will facilitate enrollment for Veterans not currently enrolled but wish to take part in the study. Exclusion Criteria: * Lacks the capacity to provide consent. * Diagnosed major medical disorder (e.g., neurological disorder, cancer, chronic infectious disease or liver disease) or has a moderate or severe traumatic brain injury, which could otherwise explain the health symptoms or interfere with their ability to safely engage in Tai Chi exercises. * Change in psychotropic or pain medication during the past month. This will minimize amount of symptom change due to medication alterations. (Once enrolled, medication changes are nonetheless expected and will be monitored.) * Regular current Tai Chi, formal mindfulness meditation program, or yoga practice, defined as at least three hours per week for more than three months. (Veterans with prior experience who do not currently engage in regular practice at this level will be eligible.) * High risk from a mental health perspective e.g., recent psychiatric hospitalization, high risk flag or a note in their VA electronic health record indicating current high-risk factors, entered into a drug or alcohol detoxification or rehabilitation program, or attempted suicide within the previous year as indicated in their VA electronic health record. * Pregnant or breastfeeding or plans to become pregnant within the year, assessed via self-report. Enrollment of pregnant or breastfeeding participants could potentially complicate outcomes, as new symptoms are likely to arise during the course of the intervention that are attributable to the pregnancy or breastfeeding and not the intervention or symptoms related to PTSD. * Reports difficulty standing on feet for the majority of a Tai Chi class (approximately 60 minutes). * Reports that they have been told by a doctor that they should not engage in physical activity unless recommended by a medical team. * Reports other reason they cannot safely participate in physical activity. * Concurrent participation in another clinical trial * Participants who engage in behavior that is disrespectful or disrupts the group may be terminated from the study. * Participants who demonstrate evidence of falsifying data may be terminated from the study