Tetanus is an acute and potentially fatal spastic paralytic disease. This case aims to describe the role of magnesium sulphate infusion in controlling muscle spasms and rigidity in a child with severe generalised tetanus in a resource-limited hospital. A six-year-old unimmunised child with severe tetanus was brought to the emergency unit of the Kalabahi Regional Hospital. The patient was treated with intramuscular human tetanus immunoglobulin, intravenous metronidazole, and ceftriaxone. Diazepam infusion was administered and gradually increased to a dose of 140 mg/day. The patient was unresponsive to diazepam, so intravenous magnesium sulphate was administered at a dose of 100 mg/kg for 30 minutes, followed by an infusion at 40 mg/kg/hour. The patient responded well to the treatment and was discharged from the hospital on day 28. Magnesium sulphate infusion can be an effective adjunctive therapy to control muscle spasms and rigidity in children with severe generalised tetanus.