A 61-year-old white female, a Jehovah's Witness, with severe pulmonary hypertension, presented with worsening heart failure symptoms. She had a pericardial effusion with left ventricular (LV) diastolic collapse on transthoracic echocardiography. She was not a candidate for surgical pericardial window and therefore underwent pericardiocentesis and percutaneous balloon pericardiotomy with remarkable improvement in her clinical condition and with no recurrence of the effusion. LV diastolic collapse, an atypical presentation of cardiac tamponade, is commonly seen in postoperative patients with localized pericardial effusions. However, outside the surgical setting, isolated LV diastolic collapse is rare. Our case is one of the first cases described in the literature of LV diastolic collapse in the setting of severe pulmonary hypertension treated successfully with pericardiocentesis and percutaneous balloon pericardiotomy.