This study focuses on the production and characterization of ferromagnetic Fe80P13C7 alloys with cobalt and/or nickel additions. Starting from the base composition of Fe80P13C7, an alloy series of Fe(80−x-y)NixCoyP13C7 (x,y = 0, 5, 10, 15, 20 at%; x + y = 20 or 0) has been synthesized using the melt spinning technique. For a fixed amount of metalloids (P13C7), three novel alloys, namely, Fe60Ni15Co5P13C7, Fe60Ni10Co10P13C7 and Fe60Co15Ni5P13C7 have been synthesized and characterized for the first time. The Fe80P13C7, Fe60Ni20P13C7 and Fe60Co15Ni5P13C7 alloys were also subjected to short-term fluxing treatment. Nine types of samples from six different alloy compositions, including three fluxed alloys, were comparatively investigated for their glass-forming abilities, compositional deviations, as well as thermal and magnetic properties.