We present a case of disseminated Pneumocystis jirovecii pneumonia in a patient with a medical history of glioblastoma multiforme associated with acute deep-vein thrombosis. The patient presented to the emergency department with clinical features of pulmonary infection, and the chest images showed pneumonia. Antibiotics were initiated (azithromycin, cefepime, and vancomycin) and the patient was transferred to the ward for further management, where the condition of the patient continued to worsen over the second day. The patient developed bilateral lower extremity swelling and the doppler ultrasound revealed bilateral lower extremity acute deep vein thrombosis. Laboratory results showed pancytopenia and transaminitis. However, a repeated chest X-ray showed ground-glass changes and interstitial infiltrates, suggestive of atypical infection. We indeed identified D-glucan which hints to a disseminated form of Pneumocystis jirovecii pneumonia infection in this patient. We further confirmed the Pneumocystis jirovecii pneumonia by polymerase chain reaction test from the fluid obtained via bronchoalveolar lavage. We, therefore, initiated intravenous trimethoprim/ sulfamethoxazole treatment with an anticoagulant, and the patient’s condition improved. Our findings strongly suggest a possible link between Pneumocystis jirovecii pneumonia infection and thrombogenesis, with impact in medical practice.