OBJECTIVE: To evaluate the clinical and cost effectiveness of a group-based memory rehabilitation programme for people with traumatic brain injury. DESIGN: Multicentre, pragmatic, observer-blinded, randomized controlled trial in England. SETTING: Community. PARTICIPANTS: People with memory problems following traumatic brain injury, aged 18-69 years, able to travel to group sessions, communicate in English, and give consent. INTERVENTIONS: A total of 10 weekly group sessions of manualized memory rehabilitation plus usual care (intervention) vs. usual care alone (control). MAIN MEASURES: The primary outcome was the patient-reported Everyday Memory Questionnaire (EMQ-p) at six months post randomization. Secondary outcomes were assessed at 6 and 12 months post randomization. RESULTS: We randomized 328 participants. There were no clinically important differences in the primary outcome between arms at six-month follow-up (mean EMQ-p score: 38.8 (SD 26.1) in intervention and 44.1 (SD 24.6) in control arms, adjusted difference in means: -2.1, 95% confidence interval (CI): -6.7 to 2.5,  = 0.37) or 12-month follow-up. Objectively assessed memory ability favoured the memory rehabilitation arm at the 6-month, but not at the 12-month outcome. There were no between-arm differences in mood, experience of brain injury, or relative/friend assessment of patient's everyday memory outcomes, but goal attainment scores favoured the memory rehabilitation arm at both outcome time points. Health economic analyses suggested that the intervention was unlikely to be cost effective. No safety concerns were raised. CONCLUSION: This memory rehabilitation programme did not lead to reduced forgetting in daily life for a heterogeneous sample of people with traumatic brain injury. Further research will need to examine who benefits most from such interventions.