Relapse is a major public health concern in the treatment of substance use disorder. Identifying effective and affordable management of relapse is important for reducing significant disruptions in the long-term recovery plan and potential frustrations for patients and their caregivers. The present randomised clinical control study explored the effect of rhythmic engagement therapy (RET), a non-pharmacological intervention, in preventing relapse among polydrug users re-admitted to a public rehabilitation facility. The study also compared the effectiveness of this intervention with cognitive behavioural therapy (CBT). This research was conducted at the National Drug Law Enforcement Agency facility in Onitsha, Nigeria. Thirty participants (10 per group), aged 18 to 60 years ( M = 31.47; SD = 9.02), were sampled for the study. These were randomly assigned into CBT and RET treatment groups, while the third group was the control. Data were collected using the Drug Abuse Screening Test (DAST) and the Short Alcohol Dependence Data Questionnaire (SADD) before and after the intervention that lasted for 3 (three) months. The result from DAST revealed a significant mean difference in the comparative effects of RET and CBT in relapse prevention. Clients who received RET showed a significantly greater reduction in relapse compared to the CBT group with a large effect size (η2), F(2, 26) = 33.88, p < .001; Cohen’s d = .723. Also, the result from SADD showed that there was a significant main effect of RET and CBT interventions on relapse after the pretest was controlled, at F(2, 26) = 25.13, p < .001 with a moderate effect size (Cohen’s d = .659). This study recommends incorporating these intervention methods into routine treatment techniques for substance use relapse management and draws attention to further research on RET.