A series of directly electrodeposited nickel–nickel oxide core–shells (NiNiO) on a glassy carbon electrode (GCE) have been prepared by the variation of cycle number through a facile electrochemical deposition method using a cyclic voltammetry (CV) technique in HCl solution and have been used as a highly sensitive enzyme-free glucose biosensor in 0.1 M NaOH. The characterizations of the biosensor probe revealed that the Ni-core forms as a homogeneous nanoparticle structure during the deposition, and then the NiO-shell is formed on the Ni-core. The electrochemical activity of the modified electrode towards the oxidation of glucose was studied using various electrochemical methods. Under optimum conditions, the glucose biosensor exhibited a long linear-range of glucose concentrations from 2 μM to 14 mM and a lower detection limit of 0.4 μM (S/N = 3), associated with excellent stability, high reproducibility, and favorable selectivity against common interferents. Very importantly, it showed an ultra-fast response time (∼1 s) and higher sensitivity (1889.8 μA mM⁻¹ cm⁻²) than that ever reported for an electrodeposited Ni-based biosensor for glucose oxidation. Moreover, the proposed method was successfully applied to determine glucose in real samples with satisfactory results.