Calcium channel blockers and magnesium sulfate are frequently used together, particularly in women with underlying chronic hypertension and pre-eclampsia. A review of the literature showed prolonged neuromuscular blockade after treatment with magnesium sulfate. Since magnesium and calcium have opposite effects on the neuromuscular junctions, muscle weakness may become a postoperative manifestation of magnesium sulfate and calcium antagonist treatment in the obstetric population; however, limited information is available regarding this postulation. Here, we report a case wherein rocuronium activity was markedly prolonged due to pretreatment with magnesium sulfate and nicardipine after general anesthesia during an emergency cesarean delivery.