The fast neutron and gamma-ray attenuation characteristics of high-density polyethylene (HDPE) reinforced with boron carbide (B4C), iron oxide (α-Fe2O3), aluminum oxide (Al2O3), iron (Fe), and aluminum (Al) particles were investigated for use as neutron radiation shielding materials. The samples were fabricated from Pure HDPE, HDPE/10% B4C, and HDPE/10% B4C/30% X (X= Fe, Al, α-Fe2O3, and Al2O3) using the compression molding technique. Scanning electron microscope (SEM) has been used to characterize the prepared samples. The mechanical properties of the prepared samples have been investigated. Sample C3 (HDPE/10% B4C/30% α-Fe2O3) shows better mechanical properties than other samples under investigations. 239Pu–Be was used as a source of fast neutrons with a neutron yield of 1.7x106 n/sec and were detected by the Stilbene scintillator. Neutron removal cross-section (ƩR) with dependent parameters, mean free path (MFP) and half-value layer (HVL), of the prepared composites were calculated. In addition, the gamma-ray transmission through the prepared composites has been investigated. As a result, the composite containing 30% iron oxide showed better shielding properties for both neutrons and gamma-rays compared to the other investigated samples. The calculated values of the shielding parameters revealed that the prepared composites can be efficiently used in fast neutrons and gamma rays shielding in fields that use radiation facilities.