Acute generalized exanthematous pustulosis (AGEP) is a rapidly evolving, febrile, widespread, non-follicular pustular eruption mainly provoked by drugs. Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor containing a sulfonamide substitute, is now clinically widely used due to its advantage of lower rate of gastrointestinal irritation. We report a case of AGEP in a 61-year-old woman who presented with fever, widespread maculopapules, vesicles, bullae, tiny pustules and leukocytosis soon after the ingestion of celecoxib. The condition resolved rapidly within 10 days. AGEP was diagnosed based on clinical and histopathological findings. Skin patch testing showed positive reaction to 1% celecoxib without cross-reactivity to 1% sulfamethoxazole-trimethoprim.