Background: The prevalence of Substance Use Disorder (SUD) in people with Mild Intellectual Disability and Borderline Intellectual Functioning (MID-BIF) is high and evidence-based treatment programs are scarce. The present study describes the development of a personalised SUD treatment for people with MID-BIF. Method: The personalised SUD treatment is developed according to the steps of the Intervention Mapping approach, based on literature review, theoretical intervention methods, clinical experience and consultation with experts in the field of addiction and intellectual disability care. Results: We developed a treatment manual called Take it Personal!+. Take it Personal!+ aims to reduce substance use, is based on motivational interviewing and cognitive behavior therapy and personalised based on the client's personality profile. Furthermore, an mHealth application supports the treatment sessions. Conclusion: Take it Personal!+ is the first personalised SUD treatment for individuals with MID-BIF. Future research should test the effectiveness of Take it Personal!+ in reducing SU.