Glyphosate is the active ingredient in widely used herbicides. It acts through inhibition of the shikimate metabolic pathway in plants. This pathway does not exist in mammals, however, so glyphosate is presumably less toxic to humans. Nevertheless, fatal cases of glyphosate poisoning in humans have still occurred. Cases of glyphosate poisoning reported in the previous literature were almost always caused by intentional ingestion. Therefore, intramuscular injection of glyphosate with suicidal intent has not been reported. We report a case of 43-year-old man with poisoning due to intramuscular injection of glyphosate herbicide. He was admitted to the emergency department with a chilling sensation, local hotness, swelling, and tenderness at the site of glyphosate injection. He was treated with intravenous antibiotics and analgesics for 10 days and was discharged without any other complication.