Progressive macular hypomelanosis (PMH) is an acquired disorder of skin pigmentation, which is mostly under-diagnosed. It is characterized by nummular hypopigmented lesions appearing on the trunk in young persons. Several treatment options are available, although topical clindamycin and benzoyl peroxide have been used traditionally. However, good results have recently been achieved using narrow-band ultraviolet B (NBUVB) phototherapy. We present the case of a 13-year-old girl with hypopigmented lesions on the trunk and limbs that had progressed over 1 year and that were diagnosed as PMH. The patient was initially treated with topical clindamycin and benzoyl peroxide. However, little improvement was seen and treatment was then started with NBUVB phototherapy. After 25 sessions, with a total cumulative dose of 18 J/cm2, the patient showed almost total repigmentation of the lesions. The treatment of PMH is often difficult, and very little is currently known about the treatment response in this disorder, as most reports have very small series of patients with a short disease progression time. NBUVB phototherapy has been shown to be effective, as seen in our patient, although in many cases, there is recurrence after the cessation of treatment.