We present a case of inadvertent arterial insertion of a central venous catheter, identified during a pericardiectomy procedure after observing abrupt changes in pressure waveform and confirmed via arterial blood gas analysis and transesophageal echocardiography. Central venous pressure measurement was initially 20 mmHg in supine, and then elevated to 30-40 mmHg in right lateral decubitus, presumably resulting from constrictive physiology of pericarditis. The pressure waveforms, however, abruptly changed from a venous to an arterial waveform during surgery. When visual discrimination between arterial and venous blood regurgitation is unreliable, anesthesiologists should confirm that using all the available methods one has on the scene, especially after at least two unsuccessful attempts or in patients with advanced age or clinical conditions resulting in jugular venous dilation. To prevent arterial catheterization, one should limit the leftward rotation of the head by <40° and consider using ultrasound-guided method after more than two unsuccessful attempts.