Background: Mediastinitis is a severe complication after cardiac surgery. While improvement of prophylaxis and of medical and surgical therapy has reduced its incidence, the treatment of mediastinitis continues to be a challenging problem. Within this study, we report the successful use of daptomycin as supportive therapy in patients developing mediastinitis after open cardiac surgery. Methods: The records of 21 consecutive patients who developed mediastinitis after cardiac surgery were retrospectively reviewed. After diagnosis, all patients received surgical debridement and antibiotic therapy with daptomycin. All patients were followed up to death or discharge. Results: Clinical improvement after combined surgical and antibiotic therapy with daptomycin was found in 90.5% of the patients. The median time until clinical improvement occurred was 5 [4/6] days. Daptomycin was well-tolerated and no major adverse events during therapy were observed observed. Conclusions: This study provides new and helpful information regarding the beneficial use of daptomycin as supportive treatment option in patients developing mediastinitis after cardiac surgery.