Skin disorders are frequent adverse events after coronavirus disease 2019 (COVID‐19) vaccination. However, the pathogenesis of these disorders is not fully understood. Here, we report a case series of cutaneous adverse events following COVID‐19 vaccination, and the results of our investigation reveal the underlying mechanism. Case 1: a 47‐year‐old female developed a wheal, confined to the COVID‐19 vaccination site, 2 days after her first injection. She was treated with topical steroids and oral antihistamines. Case 2: a 51‐year‐old female showed generalized petechial erythema accompanied by fever, genital bleeding, thrombocytopenia, liver dysfunction, and disseminated intravascular coagulation, 2 days after her second injection. She was diagnosed with vaccine‐induced macrophage activation syndrome and treated with anti‐inflammatory therapy. Immunohistological analysis of the skin eruption, in both these cases, showed infiltration of CD123 + BDCA2 + plasmacytoid dendritic cells (p‐DC). Despite the distinctive clinical features in these two cases, this finding suggests that p‐DC might be involved in different cutaneous adverse events after COVID‐19 vaccination.