Cellular cannibalism is a tumor activity where a cell is engulfed by another cell. This process promotes tumor cell survival under unfavorable conditions. The current report describes an extremely rare case of thrombocytopenia resulting from cellular cannibalism in a patient with bone marrow metastasis due to malignant pleural mesothelioma (MPM). A 77-year-old male presented with hemothorax and thrombocytopenia. He was diagnosed with MPM of the sarcomatoid cell type. However, his disease progressed rapidly and he died 11 days after admission. Bone marrow aspiration revealed metastatic MPM cells that had engulfed other blood cells. Accordingly, the observed thrombocytopenia was attributed to cellular cannibalism by metastatic MPM tumor cells. To the best of our knowledge, this is the first reported case of thrombocytopenia due to cellular cannibalism in a patient with this type of malignancy (MPM). The results suggested that although MPM rarely metastasizes to the bone marrow, bone marrow aspiration could be useful in such cases.