Seven different composites of high-density polyethylene (HDPE) were fabricated as potential flexible, lightweight and non-toxic radiation shields based on zinc oxide (ZnO) concentrations of 0%, 2%, 4%, 6%, 8%, 10% and 12%. The linear and mass attenuation coefficient (μ, μm), radiation protection efficiency (RPE) and mean free path (MFP) of the proposed HDPE-based composites were estimated. The shielding parameters, including μ, μm, RPE and MFP, of the seven samples were determined utilising eight X-ray standard radiation qualities (N-60 to N-300) at voltages of 60, 80, 100, 120, 150, 200, 250 and 300 kVp for effective energies of 47.5, 67.6, 83.3, 100, 126, 166, 218 and 266 keV, respectively. The μ results of the seven HDPE composite materials were between 0.1188 cm−1 and 0.4788 cm−1. The 12% HDPE/ZnO sample has the highest attenuation across all incident X-ray beam energies among the selected composites. The result revealed that the measured μm results align with the theoretical XCOM results for all samples, with an average error of 3.39%. Additionally, a composite containing 12% ZnO had a minimum MFP value and the highest percentage of RPE obtained from a 12% HDPE/ZnO sample with about 38.05%, compared with 17.09% of pure HDPE sample at 47.5 keV energy. This work concludes that adding ZnO to the HDPE polymer increases its shielding effectiveness for X-rays at these low energies, commonly used in radiation research and hospitals' radiology departments. In addition, increasing either the thickness or the ZnO concentration in the samples could enhance its practical usage as a radiation shield.