Ecthyma gangrenosum is a well recognized cutaneous manifestation of severe, invasive infection by Pseudomonas aeruginosa usually in immunocompromised and critically ill patients. This type of infection is usually fatal. Aeromonas infection is infrequently reported as the cause of ecthyma gangrenosum. Here we show the first case described in Italy of Aeromonas hydrophila ecthyma gangrenosum in the lower extremities in an immunocompetent diabetic without bacteraemia. A 63-year-old obese diabetic male was admitted with an ulcer on his left leg, oedema, pain and fever. Throughout his hospitalization blood cultures remained sterile, but a culture of A. hydrophila was isolated following punctures from typical leg pseudomonal-ecthyma gangrenosum lesions developed after admission. The patient, questioned again, stated that a few days before he had worked in a well near his house without taking precautions. We conclude that early diagnosis and suitable antibiotic therapy are important for the management of ecthyma gangrenosum. The typical presentation of soft tissue infection of A. hydrophila should mimic a Gram-positive infection, which may result in a delay in administration of appropriate antibiotics. Moreover, A. hydrophila should be considered a possible agent for non-pseudomonal ecthyma gangrenosum in a diabetic man with negative blood cultures, in presence of anamnestical risk factors.