Castleman disease is an uncommon cause of a neck mass. A benign lymphoproliferative disorder, it may be seen as a self-limited unicentric process or as a fulminant multicentric disease with systemic symptoms. The association between Hodgkin disease and Castleman disease has been debated extensively, but this association is rare. The associated Hodgkin disease frequently has been of the interfollicular subtype and typically has coexisted with the multicentric plasma-cell variant of Castleman disease. We report a case of mixed-cellularity Hodgkin disease of the neck in a patient previously diagnosed with hyaline-vascular-type Castleman disease who had undergone complete excision of a neck mass 2 years earlier.