Transthoracic echocardiography (TTE) is a valuable tool in the evaluation of patients with suspected air embolism. This report describes the presentation and evaluation of a critically ill woman with spontaneous air embolism occurring during a central venous catheter replacement. Bedside TTE established the diagnosis of air embolism, allowing prompt initiation of appropriate therapy. This case report highlights this uncommon but potentially life-threatening complication of central line placement and the utility of echocardiography in its evaluation.