Monitoring of circulating N-terminal proBNP (NT-proBNP) biomarkers is crucial for the diagnosis of people suffering from heart failure (HF). In this work, we describe a novel ultrasensitive NT-proBNP immunosensor for NT-proBNP detection in artificial human saliva. The surface of the developed immunosensor based on gold working microelectrodes (WEs) was biofunctionalized through carboxyl diazonium to immobilize anti-NT-proBNP antibodies. The chemical surface modification of WEs was carried out by cyclic voltammetery CV whilst the quantification of NT-proBNP biomarkers was made by electrochemical impedance spectroscopy (EIS). The immunosensor has demonstrated a linear detection response within the range 1-20 pg/mL for NTproBNP detection in artificial human saliva with a good selectivity in the presence of other interferences.