Herein, we have developed a highly sensitive non-enzymatic biosensor for the detection of the urea using nickel-manganese oxo/hydroxo metal nanoparticles on reduced graphene oxide, and these nanocomposites were made using the hydrothermal reduction method. Then, the characteristics of these nanocomposites were examined using Fourier transform infrared spectroscopy (FT-IR spectroscopy), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductive coupled plasma (ICP), XRD surface mapping, X-ray Diffraction (XRD) and transmission electron microscopy (TEM). Next, a working electrode modification process was conducted via the electro-polymerization of nanocomposites with aniline on the surface of a screen-printed electrode. We realized that reduction and blocking of all graphene oxide functional groups is important in increasing of sensitivity and prevent protonation of aniline by graphene. Finally, the sensitivity of the modified electrode to urea was evaluated by the cyclic voltammetry method. The results indicate that the sensor works within an acceptable linear range 30 μM to 3.3 mM, (R2 = 0.995, n = 3). Highly sensitivity and the limit of detection are roughly 5139.2 μA mM−1 cm−2 and 16.3 μM, respectively. The sensor demonstrated impressive stability and significant anti-interference properties. Based on these features, it can be concluded that the fabricated sensor is reliable for the non-enzymatic detection of urea.