Influenza vaccination is one of the main public health interventions to prevent influenza. Prior to vaccination, doctors should inform patients with a history of allergy about adverse drug reactions. We report the case of a 79-year-old man who presented with oral mucosal and nasal bleeding 5 days after receiving the flu vaccine and was subsequently diagnosed with immune thrombocytopenia. His symptoms improved and platelet count recovered after treatment with prednisolone and eltrombopag. Immune thrombocytopenia related to vaccination is rare. Due caution should be exercised before administering influenza vaccine to patients with thrombocytopenia or myelodysplastic syndrome-related hematologic diseases. Vaccine-related thrombocytopenia typically occurs within 2-3 weeks of vaccination. Patients with a history of thrombocytopenia should be informed about the related risks before vaccination.