Abstract Background Therapeutic intervention programs for somatic symptom disorder (SSD) show only small-to-moderate effect sizes. These effects are partly explained by the motivational problems of SSD patients. Hence, fostering treatment motivation could increase treatment success. One central aspect in SSD patients might be damage to motivation because of symptomatic relapses. Consequently, the aim of the present study was to investigate associations between motivational relapse struggle and therapeutic outcome in SSD patients. Methods We assessed 84 inpatients diagnosed with SSD in the early, middle and late stages of their inpatient treatment. The maintenance subscale of the University of Rhode Island Change Assessment-Short (URICA-S) was applied as a measure to assess motivational relapse struggle. Additionally, patients completed measures of treatment outcome that focus on clinical symptoms, stress levels and interpersonal functioning. Results The results from multiple regression analyses indicate that higher URICA-S maintenance scores assessed in early stages of inpatient treatment were related to more negative treatment outcomes in SSD patients. Conclusions SSD patients with ambivalent treatment motivation may fail in their struggle against relapse over the course of therapy. The URICA-S maintenance score assessed at therapy admission facilitated early identification of SSD patients who are at greater risk of relapse. Future studies should incorporate randomized controlled trials to investigate whether this subgroup could benefit from motivational interventions that address relapse.