We report the case of a 17-year-old boy with a mosaic trisomy 18, who was diagnosed with Hodgkin lymphoma. The patient showed only poor growth and two muscular ventricular septal defects; no facial dysmorphims were present. He was admitted to our hospital because of asthenia and weight loss; a mediastinal enlargement was found and an histological diagnosis of nodular sclerosis Hodgkin lymphoma on mediastinal biopsy was performed. Contextually, a chromosomal analysis on bone marrow aspirate and on peripheral blood revealed a mosaic trisomy 18. This result was confirmed also with cytogenetic analysis on skin fibroblasts. While there is a well-documented association between trisomy 18 and solid cell tumors, this is, to our knowledge, the first reported case of Hodgkin lymphoma in a patient with a mosaic trisomy 18, enlarging the spectrum of possible oncologic manifestations of the disease. © 2015 Wiley Periodicals, Inc.