Giant cell tumor of bone is a locally aggressive benign neoplasm, which is composed of oval or plump, spindle-shaped mononuclear cells and uniformly distributed multinucleated giant cells. Bone or cartilage matrix production by the tumor cells is usually not seen. We present a pathologically proven case of giant cell tumor, arising in the acetabulum and pubic bone, with unusual cartilage matrix production. We also discuss the differential diagnosis from a chondroblastoma as well as a giant cell-rich osteosarcoma.