We report a unique bioinspired phage nanosome as a biological template for tuning the NIR absorbance of gold nanoparticles (ФNSAu) coated on its surface. Spectroscopical analysis revealed that the presence of phage significantly enhances the optical properties of encapsulated dyes, rendering them excellent imaging agents. In vitro, studies showed the excellent photothermal transduction efficacy of the developed ФNSAu in combination with a chemotherapeutic drug, Mitoxantrone (ФNSAuM). ФNSAuM mediated photothermal therapy (PTT) using a 690 nm laser exhibited excellent anti-microbial activity against E. coli and C. albicans. In vitro and in ovo studies using zebrafish embryos revealed excellent biocompatibility, no/minimal cardiotoxicity, and enhanced internalization of phage-based nanosomes when compared with respective liposomal controls. When tested against 4T1 cell lines, the synthesized ФNSAuM exhibited significant synergistic anti-cancer activity with enhanced ROS generation and subsequent mitochondrial damage. The blood vessel rupturing potential of ФNSAuM mediated PTT has been demonstrated using an in ovo chick chorioallantoic membrane (CAM) assay, thus proving it as a potential photothermal agent. Overall, the developed phage-based nanosomes facilitated enhanced PTT efficacy, thereby showing an encouraging potential for anti-microbial and anti-cancer theranostics. © 2023 Elsevier Ltd