A pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. If it develops over a chronic period of time, the pericardium can dilate to accommodate the fluid. However, if it occurs acutely, rapid hemodynamic compromise ensues due to cardiac compression. Causes of pericardial effusion can be acute, subacute, or chronic. Indications for pericardiocentesis include therapeutic, diagnostic, or palliative. Informed consent should be obtained as there are several well-described risks. The procedure should be performed on telemetry, with appropriate intravenous access and supplemental oxygen, and under sterile precautions whenever possible. Ultrasound guidance is also recommended.