OBJECTIVE: Many existing treatments for gambling disorder grapple with the challenge of losing participants from treatment. Thus, treatments designed to increase adherence and retention would contribute significantly to the existing gambling treatment efficacy literature. Our study steps into the arena with an innovative approach. METHOD: We tested the effectiveness of cognitive motivational behavior therapy (CMBT), a treatment for gambling disorder designed not only to address symptoms but also to anchor participants throughout the treatment journey. We enrolled 46 individuals seeking treatment for gambling problems, all meeting the criteria for gambling disorder, and randomly assigned them to undergo 12 sessions of CMBT or to attend at least 12 sessions of Gamblers Anonymous (GA) meetings. RESULTS: Zero-inflated Poisson regression showed that individuals in CMBT had a 94% probability of completing treatment, with 95.7% attending all 12 treatment sessions and 91.3% completing the 6-month follow-up. Overall, individuals in CMBT gambled less money during follow-up periods relative to baseline than those in GA, CONCLUSIONS: Compared to GA, CMBT was more effective at retaining participants in treatment and reducing the amount of money gambled. For those who began treatment with low readiness to change, CMBT also decreased the severity of problem gambling, which was not the case for those referred to GA. (PsycInfo Database Record (c) 2025 APA, all rights reserved).