This article describes a case of leptospirosis in a man who returned from caving in Sarawak, Malaysia, and includes a discussion of epidemiology, pathophysiology, diagnosis, prevention, and treatment. The patient presented with symptoms of leptospirosis, which was confirmed by microhemagglutination titers. He became infected despite taking doxycycline daily for malaria prophylaxis. Leptospirosis is an important consideration in any returned traveler with fever. The spirochete spreads from animals to humans via water. Caving in tropical endemic zones may increase exposure risk due to the combination of multiple skin abrasions with immersions. Water in caves may increase infection risk because of increased water pH. Standard prophylaxis may be inadequate in cases of high-risk exposures.