OBJECTIVE: To evaluate an online intervention to support family members of individuals who sustained a traumatic brain injury (TBI). RESEARCH DESIGN: Randomized control trial. Parallel assignment to TBI Family Support (TBIFS) intervention or enhanced usual care control (TAU). Three testing timepoints: pretest baseline (T1), posttest within 2 weeks of assignment (T2), and follow-up 1 month after posttest (T3). SETTING: Online. PARTICIPANTS: Sixty-eight caregivers recruited nationally: 18 years of age or older, English speaking, providing primary caregiving to an adult family member with TBI and mild to moderate disability. INTERVENTION: Eight interactive modules providing information about cognitive, behavioral, and social consequences of TBI, training in problem-solving framework, and application exercises ( MEASURES: Proximal outcomes-program use, usability, and user satisfaction for TBIFS participants. Primary outcomes-TBI content knowledge, strategy application objective response and open-ended response, and strategy-application confidence. Secondary outcomes-appraisals of burden, satisfaction, uncertainty in mastery, guilt, and negative environment. RESULTS: Proximal outcomes-about 80% of TBIFS participants completed the posttest assessment, and 91% reported moderate to high usability and user satisfaction. Primary outcomes-greater posttest gains in TBI content knowledge for TBIFS than TAU ( CONCLUSION: TBIFS improved TBI content knowledge relative to TAU. Modifications might be needed to improve application and distal outcomes for caregivers. (PsycInfo Database Record (c) 2025 APA, all rights reserved).