Previous researches suggest that addressing alexithymia and emotional dysregulation in patients with alcohol and drug addiction is important. However, interventions focused on emotional problems in Substance Use Disorder (SUD) patients are rare in Japanese hospital settings. In 2014, we developed and implemented an intervention called the Serigaya Collaboration for Open heart Project (SCOP) for those SUD inpatients who have difficulty recognizing and expressing their emotions. The SCOP consists of a series of emotion-focused group psychotherapies provided by psychologist, occupational therapist, and nurse. The purpose of this preliminary study is to assess the efficacy of.SCOP in SUD patients. A total of 65 inpatients (37 alcohol and 28 drug use disorder) participated in the research. Thirty-two patients consented to receive the SCOP intervention concurrently with treatment as usual (TAU), while the rest of the patients (n = 33) received only TAU. TAU consists of cognitive-behavioral group therapy, psychoeducational group sessions, occupational therapy, and on-site self-help group attendances. Based on medical records, we assessed retrospectively the 6 months prognosis after discharge. A comparison was made between the SCOP and TAU groups in terms of treatment retention, attendance at self-help group meetings, -and alcohol or drug relapse. No dif- ference in post-discharge treatment retention was observed between the groups. The SCOP group had more self-help group attendees and fewer patients with alcohol or drug relapse than the TAU group. Although our present study is retrospective in design, our preliminary findings suggest that the SCOP intervention which focuses on emotions may be effective in encouraging SUD patients to join self-help groups, and helped prevent alcohol or drug relapses.