In a patient with mediastinitis after cardiac surgery Paenibacillus pasadenensis was detected in his sternal wound. Paenibacilli are gram-positive, aerobic, bacteria related to bacilli. Until recently these organisms were not known to cause human disease. A few cases of human infection caused by another member of this genus, P alvei, have been reported. The authors describe the first infection with P pasadenensis in humans. P pasadenensis was detected by broad-range bacterial 16S rRNA PCR. Treatment consisted of surgical debridement and antibiotics, vancomycin and ciprofloxacin followed by clindamycin and ciprofloxacin, resulting in complete recovery.