Purpose: The purpose of the study was to determine the effect of the implementation of Contingency Management (CM) intervention in a mandatory treatment center in Malaysia. Treatment engagement within psycho social sessions and treat- ment motivation were monitored in a randomized controlled trial study. Methodology: A total of 44 patients were chosen as participants and randomly assigned into two groups namely the experimental group of treatment as usual + contingency management (TAU+CM) (n=22) and the controlled group of treatment as usual (TAU) (n=22). The TAU+CM group followed a 12-week CM intervention and 4-week maintenance period without CM reinforcement. Meanwhile, the TAU group went through 16 weeks of usual psychosocial session implemented in the center. Measurements: The main outcome of the research was the effect of CM toward treatment engagement within treatment session and a secondary analysis to measure the patients' treatment motivation using Treatment Motivation Questionnaire (TMQ) during pre, post, maintenance phase and follow up after four months. CM reinforcement using reward stickers with monetary value were contingent with every achieved treatment engagement behavior. No reward was given to the TAU group. Findings: CM found to be effective on treatment engagement of the patient and has a significant effect on motivation especially toward internal motivation. Conclusion: CM proven to be effective in improving patients' treatment engagement and patients' motivation internally compared to the usual program.