Localized pagetoid reticulosis, also known as Woringer-Kolopp disease, is an uncommon cutaneous lymphoproliferative disorder classified as a solitary variant of mycosis fungoides. We describe a case of localized pagetoid reticulosis that occurred in early childhood. A 6-year-old boy presented with an erythematous plaque on the left thigh. His parents had first noted brownish erythema of his thigh a few months after birth. The size and elevation of the plaque gradually increased. Physical examination showed well-demarcated reddish plaque, 6.2 × 2.3 cm, with central erosion. Histopathological examination showed an epidermotropic infiltrate of medium atypical lymphocytes with hyperchromatic and pleomorphic nuclei. The atypical cells infiltrated as individual cells or clusters in the epidermis. Immunohistologically, the phenotype of the atypical cells was CD3⁺, CD4^–, CD8⁺, CD45RO⁺, CD20^–, CD30^–, and CD79a^–. We discuss the characteristics of this rare disease, including the differential diagnoses.