We investigated the histopathological effects of metamizole sodium (MS) on the sciatic nerve.This study was performed using 48 adult male Wistar albino rats. Ten groups were constituted with 6 rats in each group. MS injection into the sciatic nerve (group 1), MS injection into the muscle [group 3 (50 mg/kg, 0.4 ml) and group 5 (50 mg/kg, 0.8 ml)], MS injection into the muscle cavity in the vicinity of the sciatic nerve [group 2 (50 mg/kg, 0.4 ml) and group 4 (50 mg/kg, 0.8 ml)], normal saline injection into the muscle in the vicinity of the sciatic nerve [group 6A (0.4 ml) and 6B (0.8 ml)], subjected to injury by drilling the entire layer of nerve without injecting any drug, normal saline injection in the sciatic nerve, and control group. Nerve and muscle samples were taken 7 days after administrations. Tissue sections were stained using a hematoxylin and eosin-Luxol® fast blue stain, assessed by a histologist.The levels of axonal degeneration of the rats in groups 1, 2, 3, 4, 5, 6A, and 8 were found to be significantly higher compared to the levels of the rats in the control group (P<0.05). Myelin degeneration of the rats in all groups was found to be significantly higher compared to myelin degeneration of the rats in the control group (P<0.05).It was observed that MS could lead to injury in the sciatic nerve with a toxic effect due to diffusion.