A man in his late 40s presented with new difficulty holding objects in his left hand while performing bimanual tasks. One year prior, he had undergone resection of a right frontoparietal oligoastrocytoma localized adjacent to the primary motor cortex that controls left-hand movement (Figure, A) followed by adjuvant radiation and chemotherapy. No previous left-hand or right-hand motor deficits were reported. On examination, the patient was asked to move his right index finger, little finger, and middle finger sequentially. Involuntary identical left-hand movements accompanied voluntary right-hand movements (Video). A diagnosis of left-hand mirror movements (MM) was established. Magnetic resonance imaging (MRI) revealed scar formation or residual infiltrative tumor adjacent to the resection cavity and extending into the corona radiata and corpus callosum (Figure, B and C). The patient was monitored with surveillance MRI, which showed no radiographic evidence of progression over the next 2 years. His left-hand MM have persisted.