Skin lesions are frequent in human T-cell lymphotropic virus type 1 (HTLV-1) infection and may constitute an alert for the diagnosis of this condition. The most severe skin diseases related to this virus are adult T-cell leukemia/lymphoma (ATLL), an aggressive form of leukemia/lymphoma that fails to respond to chemotherapy, and infective dermatitis associated with HTLV-1 (IDH), a severe and recurrent form of eczema occurring in childhood. ATLL affects the skin in 43–72% of cases. In this review, the clinical, histopathological and immunohistochemical aspects of ATLL and IDH will be discussed, as well as the differential diagnoses, giving particular focus to the primary cutaneous ATLL. IDH may progress to HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and to ATLL. Adult onset IDH and reactional and inflammatory dermatoses found in carriers and also in patients with HAM/TSP will be considered. Other dermatological diseases that occur more frequently in HTLV-1-infected individuals such as xerosis, acquired ichthyosis, seborrheic dermatitis and infectious and parasitic dermatoses will also be discussed.