Periosteal chondroma is a slow growing benign chondroid tumor. It erode the surface of cortex and induce a saucer shape defect. Histologically, it occasionally show hypercellularity, mitosis which can lead to the erroneous diagnosis of malignant tumor. Clinical, radiographic and pathological investigations are necessary to establish the diagnosis. Marginal excision proved an effective treatment. To our knowledge, this benign chondroid tumor of humerus has never been previously reported in Korea. We report a case of periosteal chondroma of proximal humerus mimicking periosteal chondrosarcoma.