Background Global COVID‐19 pandemic has affected cancer care systems. Recent studies show that the number of cases diagnosed with cancer has drastically decreased compared to the same period before the pandemic. Therefore, we are confronted with delayed diagnosis of critical cancers. Aim The aim of this study is to investigate whether the stage of known cancers has been affected by delayed diagnosis and to compare the stages of head and neck cancers diagnosed during and before the pandemic. Methods The present study was conducted on 132 patients with malignant head and neck tumors referred to the otolaryngology, head and neck cancer department of Taleghani Hospital from 2019 to 2021. The stage of cancers was compared between two groups of patients with head and neck malignancy referred to the Otolaryngology, Head and Neck Department of the Taleghani Hospital before and during the COVID‐19 outbreak. Results The results from tumor (T), nodes (N), and metastases (M) (TNM) staging ( p ‐value = .015) and T score (value = 0.045) showed that the stage of tumor diagnosed in patients during the COVID‐19 pandemic significantly increased compared to patients diagnosed with a tumor before pandemic. Conclusion In the present study, it was observed that the early symptoms of malignant head and neck tumors have been neglected by patients during COVID‐19 pandemic and resulted in delayed diagnosis. This result may be explained by the fear of COVID‐19 infection in patients, which discouraged them from visiting a doctor at healthcare centers.