A mediastinal tumor is a neoplasm in the central area of the chest cavity, which can cause various symptoms and serious complications, including obstructive shock. A 38-year-old patient developed chest tightness and shortness of breath for no apparent reason. Chest CT revealed a mediastinal mass, which the patient initially ignored, but worsening dyspnea led to hospitalization in the emergency department. The tumor was compressing the heart and major vessels, was unresectable, and its infection caused obstructive shock. After anti-infective treatment, symptomatic management and monitoring, X-rays and CT scans showed tumor shrinkage. Obstructive shock from mediastinal tumor infection is rare. CT scans, continuous cardiac output monitoring using a pulse catheter (PICCO) and laboratory indicators are key to early diagnosis.