Bimetallic nanoparticles have received much attention recently due to their multifunctional applications, and synergistic potential at low concentrations. In the current study, bimetallic boron oxide–zinc oxide nanoparticles (B2O3–ZnO NPs) were synthesized by an eco-friendly, and cost-effective method through the utilization of gum arabic in the presence of gamma irradiation. Characterization of the synthesized bimetallic B2O3–ZnO NPs revealed the successful synthesis of bimetallic NPs on the nano-scale, and good distribution, in addition to formation of a stable colloidal nano-solution. Furthermore, the bimetallic B2O3–ZnO NPs were assessed for anticancer, antimicrobial and antioxidant activities. The evaluation of the cytotoxicity of bimetallic B2O3–ZnO NPs on Vero and Wi38 normal cell lines illustrated that bimetallic B2O3–ZnO NPs are safe in use where IC50was 384.5 and 569.2 μg ml−1, respectively. The bimetallic B2O3–ZnO NPs had anticancer activity against Caco 2 where IC50was 80.1 μg ml−1. Furthermore, B2O3–ZnO NPs exhibited promising antibacterial activity againstE. coli,P. aeruginosa,B. subtilisandS. aureus, where MICs were 125, 62.5, 125 and 62.5 μg ml−1respectively. Likewise, B2O3–ZnO NPs had potential antifungal activity againstC. albicansas unicellular fungi (MIC was 62.5 μg ml−1). Moreover, B2O3–ZnO NPs displayed antioxidant activity (IC50was 102.6 μg ml−1). In conclusion, novel bimetallic B2O3–ZnO NPs were successfully synthesized using gum arabic under gamma radiation, where they displayed anticancer, antimicrobial and antioxidant activities.