A 7-year-old, castrated male, Dachshund dog initially presented with locked-jaw syndrome. Computed tomography and magnetic resonance imaging indicated bilateral lymphadenopathy, but no skeletal or joint disorder was suspected. The dog showed no evidence of masticatory muscle myositis in the masticatory muscle antibody test and histopathologic examination, indicating non-infectious inflammation. Temporomandibular disorder due to immune-mediated disease was suspected, and the symptoms improved following prednisolone treatment. One year later, the dog was referred with multiple joint swellings and fever. Based on radiographic findings, synovial fluid analysis, and positive results of the antinuclear antibody test, systemic lupus erythematosus was diagnosed. The previous temporomandibular disorder might have been caused by systemic lupus erythematosus showing typical characteristics of recurrence and instability of various musculoskeletal systems. The symptoms were also relieved by glucocorticoid treatment. This report describes a case of systemic lupus erythematosus in a dog that was previously treated for temporomandibular disease, implying that systemic lupus erythematosus might be a cause of temporomandibular disorder or the two diseases might be associated in dogs.