Given their substantial neutron capture cross-section, extreme hardness, and high chemical and thermal stability, boron-based materials are widely used as building blocks to protect against highly ionizing radiations such as gamma rays and neutrons. Indeed, uncontrolled nuclear radiation exposure can be highly hazardous to radiation workers and the general public. In this sense, this work presents an extensive study and experimental evaluation of the nuclear shielding features of boron carbide (B 4C) based nanocomposite, where bisphenol-A based polybenzoxazine (BA-PBz) was used as matrix. The latter was used for its wide range of interesting properties that overcome some of the shortcomings of conventional phenolic resins. A two-pot synthesis process was adopted for the synthesis of (BA-Bz) monomer. Moreover, the boron carbide nanoparticles were treated with a silane (KH-560) coupling agent in order to improve the intramolecular interactions with the polymeric matrix. The neutron shielding studies were carried out at the Nuclear Research reactor of Algeria NUR. The results showed that the developed boron carbide-based nanocomposite exhibits intriguing shielding performances and good thermal stability. The highest performances were obtained at a B 4C concentration of 5. wt %, where the macroscopic cross section was found to be (Σ = 3.3878 cm −1) with a screening ratio of (S = 97.78%).