We report the case of a 59-year-old man with squamous cell carcinoma (SCC) of the right mandibular gingiva, who presented with bilateral cervical lymphadenopathy (CLA) after mRNA coronavirus disease 2019 (COVID-19) vaccination. The patient was diagnosed. Imaging studies performed prior to surgery revealed bilateral CLA and axillary lymphadenopathy (LA) ipsilateral to the vaccination site. Fine-needle aspiration (FNA) biopsy of the left CLA revealed reactive lymph nodes. The patient underwent surgical intervention for the malignant tumor, and the specimen was sent for histopathologic evaluation. The biopsy-proven cancer stage was pT3N0Mx. Positron emission tomography (PET-CT), performed six months after surgery, showed persistent bilateral CLA. However, FNA of the left axillary LA once again showed no evidence of metastasis or recurrence. Since the treatment plan may change based on the type of LA, it is important to figure out whether an mRNA vaccine has been administered to patients with head and neck cancer.