Retreatment of recurrent or second primary head and neck cancers occurring in a previously irradiated field is complex. Few guidelines exist to support practice. We performed an updated literature search of peer-reviewed journals in a systematic fashion. Search terms, key questions, and associated clinical case variants were formed by panel consensus. The literature search informed the committee during a blinded vote on the appropriateness of treatment options via the modified Delphi method. The final number of citations retained for review was 274. These informed 5 key questions, which focused on patient selection, adjuvant reirradiation, definitive reirradiation, stereotactic body radiation, and reirradiation to treat nonsquamous cancer. Results of the consensus voting are presented along with discussion of the most current evidence. This provides updated evidence-based recommendations and guidelines for the retreatment of recurrent or second primary cancer of the head and neck.