Fibrous hamartoma of infancy is a rare, benign soft tissue tumor that typically occurs within the first two years of life. The histogenesis is unclear. It is most commonly found in the axilla, shoulder, inguinal region, and chest wall and is usually a solitary malformation located in the subcutaneous tissue or reticular dermis. Local recurrence is uncommon and treatment is largely successful by local excision. The clinical course is typically benign and prognosis excellent. We describe a 7-month-old male with a mass on his left arm that progressively increased in size. The management of a subcutaneous mass in the pediatric patient presents a clinical challenge. The differential diagnosis includes numerous benign and malignant soft tissue tumors. The physical appearance and characteristics of a subcutaneous mass on a child may suggest a malignant process; however, Fibrous Hamartoma of Infancy should be included within the differential diagnosis.