A new method for preparing thin films of ternary transition metal phosphides has been developed. The ferromagnetic compound Fe3P has been doped with cobalt and tellurium by decomposing H2Fe3(CO)9PtBu with either Co3(CO)9PtBu or H2Fe3(CO)9Te via metal–organic chemical vapor deposition (MOCVD) onto a quartz substrate. Solid mixtures of the organometallic clusters were vaporized and decomposed at 400 °C to produce films that were subsequently annealed under vacuum at 650 °C for 24 h to afford crystalline films of (Fe1–xCox)3P (0.09 < x < 0.22) and Fe3(P1–xTex) (0.04 < x < 0.42). The films exhibit phase purity as confirmed by powder X-ray diffraction and X-ray photoelectron spectroscopy, which also confirmed the homogeneity of the films. Changes in elemental ratios were tracked by unit cell constants and ICP-OES analysis. Field-dependent magnetization measurements showed magnetic hysteresis with similar magnetic saturation values for each doped material. Thermogravimetric analysis was used to compare the Curie temperatures (Tc) of pristine Fe3P (thin film) and the doped films; Co-doping was found to lower the Tc by up to 7 °C and Te-doping had no observable effect on the Tc.