Background: Septic arthritis in the sternoclavicular (SC) region is rare and may be difficult to diagnose clinically and radiologically. It mainly affects immunocompromised persons, and can clinically be misinterpreted as tumor and rheumatic disorders. Lacking radiological reference standard, a multimodality approach may contribute to a prolonged diagnostic process. Purpose: To describe the diagnostics of septic arthritis in the SC region. Material and Methods: Between 2001 and 2011 10 patients with Staphylococcus infection in the SC region were investigated in our institution. Clinical, biochemical, radiological, and microbiological findings were studied retrospectively; all CT and MR examinations were re-evaluated. Results: Initial radiography in nine patients and ultrasonography in six patients were inconclusive resulting in supplementary MRI and/or CT. Five patients examined by MRI were immediately diagnosed with septic arthritis whereas CT in five patients led to the diagnosis in only one. Three were subsequently diagnosed by MRI, but delayed more than 2.5 weeks, and one was diagnosed by surgery. The median time to diagnosis was 1.5 weeks. The delay caused by imaging was 0 days to 11.5 weeks (median 0 days). By re-evaluation overlooked complications included mediastinitis in seven patients (three diffuse, four localized), and abscesses and pleuritis each in four patients. Conclusion: Awareness of infection in the SC region is important to avoid diagnostic delay. MRI is proposed as the initial imaging procedure.