Abstract <p>Snake venom has long-term physiological effects on survivor’s life. An electrochemical immunosensor based on samarium-cobalt-doped antimony tungstate (Sb₂WO₄@Sm-Co) is developed via a solvothermal method to detect snake venom antigens (SVA). The fabricated nanospheres are functionalized with carboxyl groups to enhance the linkage of the 3-mercaptopropionic acid linker (3-MPA). This modification increases the conjugation of antivenom polyvalent antibody with the nanomaterial on a glassy carbon electrode (Sb₂WO₄@Sm-Co-COOH-MPA-Ab/GCE). The modified nanospheres are characterized by UV–VIS spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The electrochemical performance of formulated immunosensor for antigen sensing is tested by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), and chronoamperometry. This developed immunosensor has a wide linear range of 5–30&#xa0;ng/mL with LODs of 0.08&#xa0;ng/mL and 0.1&#xa0;ng/mL from DPV and LSV, respectively. The amperometric immunosensor increases the tested antibody's loading capacity and accelerates the electron transfer rate. The analytical parameters reveal that this immunosensor is ultrasensitive, stable, reproducible, and selective for measuring SVA and can have potential applications in diagnostic clinics.</p> Key points <p>• <i>The hierarchical Sb</i>_<i>2</i><i>WO</i>_<i>4</i><i>@Sm-Co-COOH NPs were synthesized through&#xa0;a one-step solvothermal method</i></p> <p>• <i>Monitoring the effect of doping Sm and Co on the characteristics of Sb</i>_<i>2</i><i>WO</i>_<i>4</i></p> <p>• <i>MPA-linked IgG antibodys-based immunosensor was synthesized with good dispersity and high surface functional groups for capturing SVAs</i></p>