Fluorescent carbon nanoparticles have been gaining more attention in recent years for their excellent fluorescence properties and simple synthesis routes. Different carbon sources have been reported for fluorescent carbon nanoparticle synthesis but the use of virus particles as a carbon source is scarce. Herein, we report the utilization of M13 bacteriophage particles as the carbon source to synthesize phage-based nanoparticles through facile, one-step microwave heating. M13 bacteriophage is a nanosized filamentous virus particle with a single-stranded DNA genome encapsulated by a large number of coat proteins. These amino acid rich building blocks provide a substantial amount of carbon source for the synthesis of fluorescent nanoparticles. The resulting nanoparticles from M13 bacteriophage showed good water solubility and exhibited bright blue luminescence. The selectivity and sensitivity of the phage-based nanoparticles towards Fe(iii) ions showed a quenching effect with a linear correlation and a detection limit of 8.0 μM. This process highlights the potential application of virus particles as a source for the synthesis of fluorescent carbon nanoparticles and the sensing application.