Objective <p>This study aimed to estimate the prevalence of periodontal diseases (PD) in individuals with head and neck cancer (HNC), as well as to determine the severity of periodontitis.</p> Methods <p>The group of participants consisted of 47 individuals with HNC, with a median age of 63&#xa0;years, with a predominance of males (82.2%). All individuals underwent a complete periodontal examination, including the Bleeding on Probing Index (BSI), Plaque Index (PI), Probing Depth and Clinical Attachment Level (CAL). Statistical analyses included descriptive methods, Chi-square tests for categorical associations, and the Mann–Whitney U test to compare PI and BPI between patients with and without PD. No multivariate models were applied.</p> Results <p>The prevalence of periodontitis in the sample was 80.9% (40/49) and statistically significant differences were found between the BSI of patients with periodontal disease and the BSI of patients without periodontal disease. In the group of individuals with poor prognosis for cancer, 86.6% had some degree of periodontitis (<i>p</i> = 0.03).&#xa0;</p> Conclusion <p>Individuals with HNC had a high prevalence of periodontitis and a positive association was found between PD and worse prognoses for HNC.</p>