We herein report the case of a 77-year-old woman who developed acute thrombocytopenia during the 23rd cycle of modified FOLFOX therapy. She developed a hypersensitivity reaction with nasal bleeding. The chemotherapy infusion was immediately discontinued. The patient's symptoms resolved with discontinuation of chemotherapy and the administration of supportive therapy. A complete blood count showed severe thrombocytopenia, and oxaliplatin-induced thrombocytopenia was diagnosed. The patient was admitted to the hospital, and the thrombocytopenia was corrected with a platelet transfusion followed by prednisolone. She was discharged after one week without requiring additional platelet transfusions. With the widespread use of oxaliplatin, the risk of oxaliplatin-induced acute thrombocytopenia should be considered an acute onset hematological emergency.