Jaundice, conjunctival hyperemia, and acute kidney injury (AKI) are the characteristics of leptospirosis. However, it is not well known that Fusobacterium necrophorum infection can have a clinical picture similar to that of leptospirosis. A 38-year-old man was admitted with jaundice, conjunctival hyperemia, and AKI for 7 days. Chest CT scan showed multiple pulmonary nodules, atypical for leptospirosis. We started treatment with IV piperacillin-tazobactam and minocycline. He became anuric and was urgently started on hemodialysis on the second hospital day. Later on, blood cultures grew Fusobacterium necrophorum and other anaerobic bacteria. Antibody and PCR assays for Leptospira were negative. We narrowed the antibiotics to IV ceftriaxone and metronidazole. He responded well to the treatment and was discharged on the 18th hospital day. F. necrophorum infection is known to cause mixed infection with other anaerobic bacteria. The resistance of many anaerobic bacteria continues to progress, and F. necrophorum itself sometimes produces β-lactamase. This case highlights the potential risks of using penicillin before diagnosis of leptospirosis.