Background: Chronic graft versus host disease (cGVHD) is a major cutaneous complication of bone marrow transplantation (BMT). Although milder forms of this process may be associated with a lower incidence of tumor recurrences, it is mandatory to develop a more efficient and less harmful therapeutic approach.Methods: This case-series study enrolled 7 patients diagnosed with chronic mucocutaneous GVHD. We divided the patients into three major categories based on the type of skin lesions: sclerodermoid, lichenoid, and mixed. Patients received several packs of narrow band UVB (NBUVB) phototherapy. Each pack contained ten sessions of NBUVB (311 nm) with a duration of at least ten seconds and a fixed radiation dosage (6 mj/cm2) during the treatment.Results: There were 3 patients diagnosed with lichenoid skin lesions, 2 with sclerodermoid lesions, and 2 had mixed cGVHD lesions. During the follow up period one patient was excluded due to a lower respiratory tract infection. The mean response ratio was 42% with a mean satisfaction level of 5.5 out of 10. The lichenoid group had the best, most rapid response. There were no serious adverse effects reported.Conclusion: Narrow band UVB phototherapy is useful as an adjuvant therapeutic modality in cutaneous lichenoid and intraoral cGVHD with no serious adverse effects.