The COVID-19 pandemic has increased mRNA vaccine usage and revealed various cutaneous adverse events, such as injection site reactions, urticaria, and morbilliform eruptions. Multiple centers have reported erythema multiforme (EM) as a COVID-19 vaccine-associated adverse event. Our center observed two cases of EM in patients receiving immune checkpoint inhibitors (ICI) after COVID-19 vaccination. Notably, ICI administration is known to cause cutaneous adverse events, including EM. A previous report indicated that administering COVID-19 vaccination to patients receiving ICI treatment could promote severe systemic symptoms. This raise concerns that COVID-19 vaccination might rapidly worsen skin rashes in these patients. Our report demonstrates that skin rash related to COVID-19 vaccine-induced EM in ICI-treated patients does not significantly differ from that of COVID-19 vaccine-related EM. Additionally, in both cases, the skin rash resolved without exacerbation. Further research is necessary to determine optimal management strategies. However, our findings provide reassurance that COVID-19 vaccination is safe in ICI-treated patients and should not be avoided.