Leptospirosis is a common zoonotic disease with a worldwide distribution. Dogs become infected by exposure to contaminated urine from shedding wild animals. The bacteria penetrate mucus membranes, causing endothelial damage and damage to organs, such as the liver and kidneys. The clinical signs and clinicopathologic data are nonspecific and a high index of suspicion is needed by the practitioner. Testing today is highly based on serology (microscopic agglutination test) and perhaps polymerase chain reaction. Treatment of leptospirosis involves supportive care and antibiotics, and prevention includes environmental steps and annual vaccination of dogs at risk.