Inclusion Criteria:

• * Enrollment in the Traumatic Brain Injury Model System (TBIMS) from one of the six referring centers.
• * Must be between 18-64 years of age at the time of enrollment.
• * Must have cognitive capacity to consent.
• * Must be \>1 year out from the date of the Traumatic Brain Injury.
• * Meet the -5 criteria for major depressive disorder (as determined by the Mini International Neuropsychiatric Interview (MINI)).
• * Must receive a Health Contribution Score (HCS) of \<24 on the Godin Leisure Time Exercise Questionnaire.
• * Deemed medically safe to exercise (based on the Physical Activity Readiness Questionnaire (PAR-Q+) modified (if a yes response to any question, physician attestation required).
• * Must have a permanent residence and have access to the internet.
• * We will over-enroll people who identify as African American because they are at higher risk of depression and face disproportionate barriers to treatment relative to whites. We chose to over-sample African Americans rather other racial or ethnic groups because they represent the second largest racialized subgroup within the full Traumatic Brain Injury Model Systems (18%) and 27% of those with Major Depressive Disorder (MDD). Therefore, we will enroll a sample that is 27% people who identify as African American.

Exclusion Criteria:

• * We will exclude people with active suicidal intent or plan or other severe psychiatric conditions (bipolar disorder, schizophrenia, psychosis, any schizoaffective disorder).
• * We will exclude people with current substance use disorder (excluding tobacco) because they require intensive treatment, specifically people who report having \> 5 drinks for men or \>4 for women on a single occasion AND have \>14 drinks for males / \> 7 drinks per week for females per week. These questions are an existing part of the Traumatic Brain Injury Model System, Form II follow-up interview and participant exclusion for this will take place as part of that study.
• * We will exclude people for drug dependence as defined within the Mini International Neuropsychiatric Interview (MINI).
• * We will exclude people not fluent in English.
• * People with pending surgery or on an unstable dose of standard depression treatment will be deferred until they are recovered or on stable treatment regimens for at least 3 weeks.
• * To ensure safety in the trial we will exclude people who have suicide intent or plan and immediately refer them for treatment. We will measure suicide risk at every outcome assessment point and address elevated risk via established assessment and intervention protocols.