A six-month-old female turkey from a commercial growing unit was evaluated at postmortem examination for investigation of suspected viral lymphoproliferative disease. Clinically, the turkey was dull and subdued, and relatively unresponsive to external stimuli. The main gross postmortem findings were diffusely enlarged spleen, kidneys and liver, with multifocal cream foci. The lungs were atelectatic, and mild segmental mural thickening of the small intestines was observed. Impression smears taken during postmortem examination confirmed the presence of a population of neoplastic lymphocytes, which, on histological examination, infiltrated multiple organs. Using quantitative real-time PCR analysis, spleen and liver samples were positive for Marek's disease virus and negative for herpesvirus of turkeys. A splenic sample was negative for reticuloendotheliosis virus. This case report details gross, cytological and histological findings in a confirmed case of Marek's disease in a turkey where disease manifests as infiltration of numerous organs with pleomorphic neoplastic lymphocytes.