Radial artery thrombosis is a rare complication of cannulation. There are no reported cases of acute thrombosis and severe acute neuropathy in the setting of cannula discontinuation. We report a case of acute radial nerve mono-neuropathy following thrombosis after radial arterial line removal. The thrombus was immediately evident on exam and diagnostic imaging after cannula discontinuation. The patient was consented and promptly taken to OR for immediate repair. Mild radial neuropathy persisted despite immediate repair. Immediate recognition of signs and symptoms is essential for diagnosis and management, especially in the high-risk population.