BACKGROUND: Cardiac output (CO) monitoring is essential for diagnosing and managing critically ill patients. Recently, a non-invasive haemodynamic monitoring technique, electrical cardiometry (EC), has gathered increasing interest among ICU physicians. This study aimed to explore the accuracy of CO estimated by non-invasive EC (CO METHODS: This prospective, observational, single-center study was conducted from April 2021 to April 2023, involving patients who required haemodynamic monitoring using a transpulmonary thermodilution device (PiCCO). CO RESULTS: Seventy-two patients with PiCCO haemodynamic monitoring were included, yielding 285 paired CO measurements. The bias between CO CONCLUSION: In critically ill patients, non-invasive EC indicated limited accuracy in measuring CO, along with a restricted ability to reliably track CO changes. These findings suggested that EC may not be interchangeable with TPTD in the general ICU population.