A 46-yr-old female Sumatran orangutan (Pongo abelli) was first diagnosed with pericardial effusion in July 2006. Pericardiocentesis performed in January 2007 only provided short-term relief. In May 2007, a pericardial-peritoneal window was created using a transabdominal subxiphoid pericardiostomy technique, providing immediate and long-term relief. Seven months later, the orangutan was euthanized due to worsening heart failure, and no pericardial effusion was present. Transabdominal subxiphoid pericardiostomy offers a straightforward surgical approach that can provide significant relief in cases of chronic pericardial effusion in great apes.