Although cancer and ischemic heart disease (IHD) frequently manifest in the same individual, the risk of IHD events in cancer, especially head and neck cancer (HNC), remains unclear. We aimed to examine the incidence and risk of IHD events in patients with HNC using a population-based cohort dataset in South Korea (2002–2013). Through rigorous propensity score matching, we compared data from 2816 individuals without HNC and 704 individuals with HNC. Key independent variables were matched between groups, and the Charlson Comorbidity Index was used to match comorbidities. The Kaplan–Meier method depicted the cumulative probability of IHD throughout the follow-up period for both the study and control groups. The overall IHD incidence was significantly higher (19.93) in patients with HNC than in those without HNC (14.81), signifying an augmented IHD risk in the HNC cohort. Subsequent temporal analysis revealed a significant surge in IHD risk commencing 4 years after HNC diagnosis and persisting throughout the follow-up period. Subgroup analysis revealed an increased IHD risk in men with HNC and patients with cancers affecting the oral and sinonasal regions. This retrospective cohort study provides valuable scientific insights into the nuanced relationship between HNC and IHD, underscoring the need for tailored monitoring protocols and specialized care for susceptible individuals.