Abstract Thermoplastic natural rubber (TPNR) based on polybutylene adipate terephthalate (PBAT)/natural rubber (NR) has been prepared to develop flexible radiation shielding materials by adding antimony oxide (Sb 2 O 3 ). TPNR composites were prepared with a composition of NR 40% and PBAT 60%, at various loading levels of antimony oxide. The properties of the resulting composites, such as tensile strength, elongation at break, hardness, and specific gravity of TPNR composites, were investigated. Gamma‐ray shielding properties were measured under the exposure of gamma rays in the energy range of 0.223–0.662 MeV by Compton scattering technique. X‐ray shielding properties were measured with a high‐frequency digital radiography X‐ray machine at 70–120 kVp and 40 mAs. The results show that the gamma‐ray shielding properties, such as the values of mass attenuation coefficient ( μ m ), effective atomic number ( Z eff ), and effective electron density ( N eff ) of materials, increased with increasing amounts of Sb 2 O 3 . Similar results were observed for X‐ray shielding properties. The half‐value layer (HVL) values of all samples decreased with increasing Sb 2 O 3 content. The obtained results confirm that TPNR/Sb 2 O 3 can be effectively used as an alternative flexible radiation shielding material.