We present the management of agranulocytosis and neutropenic sepsis secondary to carbimazole with recombinant human granulocyte colony stimulating factor (G-CSF). A 72-year-old woman with a history of thyrotoxicosis presented with sore throat and fever two weeks after starting carbimazole. Investigations confirmed a leucopenia and neutropenia. G-CSF was used as an adjunctive therapy with discontinuation of carbimazole, barrier nursing and a broad-spectrum antibiotic regimen to treat her neutropenic sepsis. Total white cell count and neutrophil count returned to normal and she made an uneventful recovery. She was subsequently rendered euthyroid with radioiodine treatment.