The prognosis for Black patients with classical cutaneous T-cell lymphoma (CTCL) [mycosis fungoides (MF) and Sézary syndrome (SS)] is known to be worse than that of other ethnicities, but there is a paucity of data on which demographic factors or disease characteristics may contribute to this disparity. In our retrospective cohort study of 229 patients, Black patients experienced poorer overall survival adjusted for confounding variables including demographics and key disease characteristics (P = 0.01), and suffered a significantly higher rate of large-cell transformation when compared with White patients (P = 0.012). Our study suggests that Black patients with MF/SS experience poorer overall survival that cannot be explained by sex, age or CTCL disease characteristics.