Composite lymphoma implies the presence of two or more morphological and immunophenotypical subtypes of lymphoma in a single tissue or organ. Composite lymphoma with concurrent mantle cell lymphoma (MCL) and classical Hodgkin lymphoma is extremely rare. In this case report, we present the case of a 70-year-old male who was diagnosed with a composite of MCL and classical Hodgkin lymphoma (cHL) and achieved near-complete resolution with chemoimmunotherapy. To the best of our knowledge, this is the first case of this kind demonstrating the effectiveness of a combination chemoimmunotherapy regimen leading to complete remission in composite lymphoma involving MCL and cHL. We report the history, imaging findings, and pathology and illustrate the challenges in therapeutic decision-making in managing composite lymphoma patients involving MCL and cHL. We also review the literature on this rare entity and discuss its clinical implications.