Objective. To examine the efficacy of the modified Story Memory Technique (mSMT) to improve learning (ie, acquisition) and memory in participants with TBI. The mSMT is a behavioral intervention that teaches context and imagery to facilitate learning within 10 sessions over 5 weeks. Methods. A total of 69 participants with moderate-severe Traumatic Brain Injury (TBI), 35 in the treatment group and 34 in the placebo control group, completed this double-blind, placebo-controlled randomized clinical trial. A baseline neuropsychological assessment was administered, including questionnaires assessing everyday memory. Repeat assessments were conducted immediately posttreatment and 6 months following treatment. Participants in the treatment group were randomly assigned to a booster session or a non–booster session group after completion of treatment with the mSMT to examine the efficacy of monthly booster sessions in facilitating the treatment effect over time. Results. The treatment group demonstrated significant improvement on a prose memory task relative to the placebo group posttreatment (η2 = 0.064 medium effect). Similar results were noted on objective measures of everyday memory, specifically prospective memory (Cohen’s w = 0.43, medium effect), and family report of disinhibition in daily life (η2 = 0.046, medium effect). Conclusion. The mSMT is effective for improving learning and memory in TBI. Classification of evidence. Based on widely accepted classification systems for treatment study design, this study provides class I evidence that the mSMT behavioral intervention improves both objective memory and everyday memory in persons with TBI over 5 weeks. Thus, this study extends the evidence for efficacy of the treatment protocol to a sample of persons with TBI.