Acute generalized exanthematous pustulosis (AGEP) and toxic epidermal necrolysis (TEN) are both severe cutaneous adverse reactions, mostly to drugs. Although predominantly involving skin, they differ significantly in presentations, prognosis, pathology, immunogenesis, and treatment. They have very rarely been described to occur simultaneously in a patient, manifesting as AGEP-TEN overlap. We describe a 67-year-old Chinese lady with systemic lupus erythematosus who presented with features of AGEP but evolved to AGEP-TEN overlap as an adverse reaction to hydroxychloroquine (HCQ) treatment. This case is the first reported case of AGEP-TEN overlap secondary to HCQ and highlights the need for constant surveillance for rare adverse events that may manifest even after decades of use of the drug worldwide.