We report the case of a 5-month-old infant with a rapidly growing mass on the right nasolabial fold; to our knowledge, this is the youngest infant diagnosed with nodular fasciitis in the literature. Based on the anatomic location, this was a subcutaneous type of nodular fasciitis and it had a mixed cellular and fibrous histologic composition, which is rare in infancy. Here we present periodic ultrasonographic images and MR images, as well as a detailed comparison of the pathologic and radiologic findings.