BACKGROUND Incomplete recovery from residual neuromuscular block agent (NMBA) after anesthesia is a serious adverse event in the post-anesthesia care unit. Acetylcholinesterase neostigmine is usually used to reverse residual neuromuscular blockade and facilitate spontaneous breathing and endotracheal extubation. CASE REPORT A 40-year-old woman received general anesthesia for strabismus correction surgery. At the end of surgery, repeated doses of neostigmine up to 85 µg/kg failed to reverse the residual neuromuscular blockade (train-of-four [TOF] ratio below 21%). Sugammadex (200 mg) provided immediate reversal, with the TOF ratio up to 100%. The patient regained spontaneous breathing, and the endotracheal tube was removed. After surgery, myasthenia gravis was diagnosed. CONCLUSIONS When unexpected prolonged neuromuscular blockade presents, the TOF ratio should be used to detect its depth and guide a reasonable dose of reversal agents. Anticholinesterase has a ceiling effect; once acetylcholinesterase activity is fully inhibited, administration of additional anticholinesterase can result in no further recovery. Furthermore, excessive acetylcholine can cause muscle weakness. In contrast, sugammadex is a selective reversal agent for steroidal NMBA, which works by encapsulation via tight water-soluble complexes with amino steroids (eg, rocuronium) rather than increasing acetylcholine at the neuromuscular junction. In this case, the recovery from moderate neuromuscular blockade by sugammadex was more effective and rapid than that by neostigmine. When refractory and prolonged residual neuromuscular blockade presents after repeated doses of anticholinesterase, sugammadex should be considered as an effective reversal agent. Particularly in cases of myasthenia gravis, sugammadex is superior to neostigmine for reversing rocuronium-induced NMBA in patients undergoing surgery.