Agranulocytosis is a rare side effect of antithyroid drugs, it occurs in less than 0.5% of patients, usually during the first few months of treatment. It is considered to be the most serious adverse effect of these medications since it may be complicated by serious, life-threatening infections. Mucormycosis is a severe mycotic infection that usually develops in immunocompromised hosts, such aspatients with diabetes mellitus, hematologic malignancies or immunosuppressive therapy. The association of mucormycosis with methimazole-induced agranulocytosis has not been previously described. The objective of this case presentation is to analyze the case ofa woman with diffuse toxic goiter and methimazole-induced agranulocytosis who developed rhino-palatal mucormycosis.