Approximately 50% of patients with adult T-cell leukemia/lymphoma (ATLL) have skin involvement, and the smoldering, skin lesion-bearing cases are often treated with various skin-directed therapies, such as phototherapy and radiation therapy. Daily oral administration of etoposide plus prednisolone (EP) is also used for smoldering-type ATLL. However, it remains unclear whether these therapies improve patients' survival. We retrospectively analyzed the prognosis of patients with smoldering, skin lesion-bearing ATLL (n = 62), who were treated, as first therapy, with one skin-directed therapy (n = 29), oral EP alone (n = 14) or a combination of skin-directed therapy and oral EP (n = 19). Multivariate analysis revealed that the hazard ratios (HRs) for the overall survival (OS) and progression-free survival (PFS) with the combination therapy were significantly lower than those with the skin-directed therapy (HR 0.1, p = 0.001; HR 0.2, p = 0.002, respectively). These results suggest that the combination of skin-directed therapy and oral EP improves the clinical outcome of patients with smoldering, skin lesion-bearing ATLL.