Abstract Background Only 55% of multidrug-resistant tuberculosis (MDR-TB) cases worldwide complete treatment, with problem substance use a risk for default and treatment failure. Nevertheless, there is little research on psychotherapeutic interventions for reducing substance use amongst MDR-TB patients, in general, and on their delivery by non-specialist health workers in particular. Objectives To explore the feasibility and acceptability of a non-specialist health worker-delivered 4-session brief motivational interviewing and relapse prevention (MI-RP) intervention for problem substance use and to obtain preliminary data on the effects of this intervention on substance use severity, depressive symptoms, psychological distress and functional impairment at 3 months after hospital discharge. Methods Between December 2015 and October 2016, consenting MDR-TB patients admitted to Brewelskloof Hospital who screened at moderate to severe risk for substance-related problems on the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) were enrolled, and a baseline questionnaire administered. In the 4 weeks prior to planned discharge, trained counsellors delivered the MI-RP intervention. The baseline questionnaire was re-administered 3 months post-discharge and qualitative interviews were conducted with a randomly selected sample of participants (n = 10). Results Sixty patients were screened: 40 (66%) met inclusion criteria of which 39 (98%) were enrolled. Of the enrolled patients, 26 (67%) completed the counselling sessions and the final assessment. Qualitative interviews revealed participants’ perceptions of the value of the intervention. From baseline to follow-up, patients reported reductions in substance use severity, symptoms of depression, distress and functional impairment. Conclusion In this feasibility study, participant retention in the study was moderate. We found preliminary evidence supporting the benefits of the intervention for reducing substance use and symptoms of psychological distress, supported by qualitative reports of patient experiences. Randomised studies are needed to demonstrate efficacy of this intervention before considering potential for wider implementation. Trial registration South African National Clinical Trials Register (DOH-27-0315-5007) on 01/04/2015 (http://www.sanctr.gov.za)