An 84-year-old man received a 23-valent pneumococcal polysaccharide vaccine (PPV23) for the second time, and he developed fever and shortness of breath three days later. He was admitted to our hospital because of bilateral pulmonary infiltration shadows on a chest radiograph. Despite the administration of antibiotics, his symptoms did not improve, and he was placed on ventilator support. His bronchoalveolar lavage fluid (BALF) obtained by bronchoscopy revealed increased total cell counts and lymphocyte fraction. Steroid pulse therapy was initiated, which was successful, and bilateral infiltration shadows disappeared. After completion of therapy, a drug-induced lymphocyte stimulation test (DLST) for PPV23 was performed, which had positive results. These results indicate that PPV23 caused pneumonitis, according to the consensus statement for the diagnosis and treatment.