Summary Stabilisation splint therapy has long been thought to be effective for the management of temporomandibular disorders (TMD). However, the superiority of stabilisation splint therapy compared to other TMD treatments remains controversial. The aim of this study was to determine the efficacy of stabilisation splint therapy combined with non‐splint multimodal therapy for TMD. A total of 181 TMD participants were randomly allocated to a non‐splint multimodal therapy (NS) group (n = 85) or a non‐splint multimodal therapy plus stabilisation splint (NS+S) group (n = 96). Non‐splint multimodal therapy included self‐exercise of the jaw, cognitive–behavioural therapy, self‐management education and additional jaw manipulation. Three outcome measurements were used to assess treatment efficacy: mouth‐opening limitation, oro‐facial pain and temporomandibular joint sounds. A two‐factor repeated‐measures analysis of variance (anova) was used to evaluate the efficacy of the two treatment modalities (NS vs. NS+S), and Scheffe's multiple comparison test was used to compare the treatment periods. Subgroup analyses were performed to disclose the splint effects for each TMD diagnostic group. All three parameters significantly decreased over time in both groups. However, there were no significant differences between the two treatment groups in the total comparison or subgroup analyses; an exception was the group with degenerative joint disease. No significant difference between the NS and NS+S treatment approaches was revealed in this study. Therefore, we conclude that the additional effects of stabilisation splint are not supported for patients with TMD during the application of multimodal therapy.