Erythema multiforme (EM), an immune-mediated skin condition, can occur after infection or following the use of medications. In this study, we describe a patient who developed EM after nirmatrelvir/ritonavir administration. An 81-year-old woman presented with fever and dyspnea. Laboratory investigations showed positive coronavirus disease (COVID-19) based on polymerase chain reaction assay, and she received a 5-day regimen of nirmatrelvir/ritonavir. We observed development of EM after this treatment and initiated prednisone (1 mg/kg) therapy, which led to rapid improvement. Our study is the first to report EM in a patient with COVID-19, who received nirmatrelvir/ritonavir and showed a favorable response.