Late radiation-associated dysphagia (late-RAD) remains a challenge in head and neck cancer (HNC) survivorship, despite advancements in treatment methods. Although Fiberoptic Endoscopic Evaluation of Swallowing (FEES) stands as the preferred diagnostic approach for oropharyngeal dysphagia assessment in the HNC population, current studies lack a FEES-derived swallowing parameter characterization and phenotypic classification within this specific cohort. This study sought to employ FEES-based assessment to characterize swallowing safety and efficacy profiles, identify distinct phenotypes in HNC patients suffering from late-RAD, and examine potential correlations between safety and efficacy parameters. A retrospective analysis included twenty-four post-radiotherapy HNC patients evaluated using standardized FEES protocols across three bolus consistencies (liquid, semisolid, and solid). Swallowing safety was quantified using the Penetration-Aspiration Scale (PAS), while efficacy was measured via the Yale Pharyngeal Residue Severity Rating Scale (YPRSRS). Additionally, six distinct dysphagia phenotypes were characterized within the cohort. Propulsion deficit was the predominant phenotype (92%), followed by delayed pharyngeal phase (37.5%) and protective deficit (25%), with 46% of patients exhibiting multiple phenotypes. Unsafe swallowing occurred most frequently with liquid consistency (62.5%), while residue was most prevalent with semisolid (82.6% valleculae, 52.2% pyriform sinuses) and solid consistencies (92.3% valleculae, 53.8% pyriform sinuses). Significant correlations were found between penetration-aspiration and pharyngeal residue scores across consistencies ( < 0.05). FEES examination revealed distinct phenotypes in late radiation-associated dysphagia, with a predominance of propulsion deficit and significant interdependence between safety and efficacy parameters.