In this report we present the first case of Proteus syndrome associated with nephrogenic diabetes insipidus. The case is a 9-month-old girl, with macrodactyly of both feet and left hand, syndactyly of the 3rd and 4th fingers of the left hand, soft tissue masses in the paravertebral and gluteal regions, and a hyperpigmented epidermal nevus with hyperkeratosis on the left half of the body.