Leptospirosis which is caused by Leptospira species, may present with clinical features that vary from a mild flu-like illness to an acute life-threatening condition. Weil's disease, the most severe form of leptospirosis is characterized by multiorgan involvement including liver, kidney and lungs. In this report a severe Weil's disease was presented. A 43 years old male patient who had a history of swallowing water while swimming in the creek, was admitted to the hospital with the complaints of weakness, cough, bloody sputum, generalized jaundice and dark urine. Acute renal failure, bilateral lung infiltration, hyperbilirubinemia, leukocytosis and thrombocytopenia were detected, and the patient has undergone to hemodialysis. Ceftriaxone and ciprofloxacin treatment was applied to the patient after collection of blood, urine and sputum cultures and serum samples for serological tests. None of the cultures yielded pathogenic microorganisms. Microscopic agglutination test (MAT) was applied to two serum samples which were collected with 10 days interval. The first serum sample revealed antibody positivity at 1/200 titer against L.semeranga Patoc 1, while the second serum revealed antibody positivity at 1/400 titer against both L.semeranga Patoc I and L.icterohaemorrhagiae Wijnberg. By the administration of antibiotic therapy and early supportive care the patient was cured completely. In conclusion Weil's disease should be taken into consideration in the patients with multiple organ involvements.