Leptospirosis is a zoonotic disease associated with a changing global epidemiology. Recently, an increased incidence of canine leptospirosis in the northeastern United States and Canada has been associated with increasing rates of infection among reservoir hosts, such as skunks, raccoons, and squirrels, that are common in suburban settings. We describe a case of leptospirosis that provides new insight into the epidemiology, diagnosis, and pathogenesis of this disease acquired in the suburban setting. Atypical lymphocytosis corresponded to an expansion of γ-δ T cells in peripheral blood. © 2006 by the Infectious Diseases Society of America. All rights reserved.