OBJECTIVE: Time-processing disorders in adults is a priority area for intervention. Time management program, which has been demonstrated to be effective in children with ADHD, has not been examined in adults. We anticipate the need for the development of specialized programs for adults. This is because it has been reported that time processing disorders have different patterns in childhood and adulthood. This study aimed to evaluate the therapeutic effect of a gCBT program focusing on time management for adults with ADHD. METHOD: Adults with ADHD were randomly assigned to gCBT (n = 24) or a treatment as usual group (n = 24). Outcome measures were masked clinically rated, self-reported, and family-reported ADHD symptoms. RESULTS: The gCBT group significantly reduced ADHD symptoms on all measures. CONCLUSION: Interventions focused on time management have been shown to be effective not only in children with ADHD but also in adult patients.