Diffuse-type tenosynovial giant cell tumor (D-TSGCT), previously known as pigmented villonodular synovitis, is a locally aggressive neoplasm that may arise from the synovium, bursa, or tendon sheath. D-TSGCT is usually monoarticular and can be classified into intra- and extra-articular forms, the latter of which is rarer. Here, we report a case of D-TSGCT in a 64-year-old female that involved the entire flexor and extensor tendon sheaths of both wrists. We describe the ultrasonography and MRI findings, as well as review the relevant literature.