Objectives: Head and neck cancer (HNC) patients are at high risk for late occurring radiation-related morbidity and recurrence, necessitating close long-term medical surveillance. This study identified factors associated with becoming lost to follow-up (LTFU) at a comprehensive cancer center. Materials and Methods: Patients were drawn from survivors who received radiation for HNC at a single institution between 2001 and 2018. LTFU was defined as living patients without a clinical encounter within 2 years of the data query. Results: In total, 537 patients met the inclusion criteria and 57 (10.6%) were identified as LTFU. Individual comparisons identified time since completing radiation, non-White race and being unmarried as associated with LTFU. Multiple regression identified time since treatment and being unmarried as factors associated with LTFU. A decision tree correctly sorted 89.4% using time, distance, and marital status. Conclusion: Time since radiation, distance to clinic, and being unmarried were factors associated with becoming LTFU.