In present study, we developed a highly sensitive, electrochemical immunosensor based on fullerene C-60-modified disposable graphite paper (GP) electrode for determination of Suppression of Tumorigenicity 2 (ST2) in human serum. The synthesis of the ST2 immunosensor was monitored with electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) techniques and single frequency impedance (SFI) technique which is utilized for the specific interaction between anti-ST2 and ST2 antigen. Moreover, the morphological alteration of each GP surface was examined by scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). All parameters such as fullerene C-60 concentration, antibody concentration and antibody incubation time were optimized. Analytical characteristics such as linear determination range, repeatability, reproducibility, regeneration and surface coverage were determined for the immunosensor. The ST2 electrochemical immunosensor had excellent repeatability, reproducibility and a wide detection range (from 0.1 fg mL(-1) to 100 fg mL(-1)). The proposed immunosensor also had low limit of detection (LOD) and limit of quantification (LOQ) values of 0.124 fg mL(-1) and 0.414 fg mL(-1), respectively. The proposed immunosensor was applied to real samples to test applicability in clinical practice. (C) 2020 Elsevier B.V. All rights reserved.