We investigate the impact of Niobium (Nb) doping on the electronic structure, magnetic and optical properties of the bilayer hexagonal boron nitride (BL hBN) using spin-polarized density functional theory (DFT). The calculated values of formation energy reveal the structural stability of Nb-doped BL hBN. The structural parameter analysis indicates the bond length and lattices constant of BL hBN increase due to Nb doping. In addition, it is found that the energy band gap of BL hBN is reduced from 5.1 eV to 3.9 eV due to 5.5 % of Nb doping. Moreover, the obtained magnetic moment of 2 μ B and 4 μ B for Nb concentrations of 5.55 % and 11.11 % respectively, indicate the turning of the paramagnetic behavior of pure BL hBN to ferromagnetic. Besides, we have also found that the first and second nearest neighboring (NN) magnetic interaction between two dopants (Nb atoms) is ferromagnetic. Whereas, the third nearest neighbor interaction is antiferromagnetic. More interestingly, using mean field theory together with spin-polarized DFT ferromagnetic transition temperature (T c ) of 367 K is obtained for 11.11% of Nb-doped BL hBN. Furthermore, a significant enhancement of the absorption coefficient due to Nb doping in both the visible and mid-to-far-infrared regions was observed. Based on those results, we suggest that Nb-doped BL hBN is a good candidate material for nanoelectronics, spintronics, and optoelectronics applications.