Selective extraction of valuable elements (such as V, Cr, Mn, etc.) and their compounds from metallurgical slag is in a focus of many researchers. Although vanadium may be present in slag as oxides and/or complex spinels with Fe, Mn, etc. during an alloyed steel production, the majority of vanadium in metallurgical slags typically exists as V2O5, which comprises up to 3–5 wt% of the slag in some cases. Due to the vanadium toxicity, these slags are forbidden in many civil engineering applications. As a result, hundreds of thousand tonnes of V2O5‐bearing slags are landfilled every year. In the present work, the formation of vanadium ferrites (FeV2O4 and Fe2VO4) in synthesized CaO–SiO2–FeO–V2O5 slags containing 5 wt% V2O5 was examined under different partial pressures of oxygen. For the current slag chemistry range, an XRD analysis confirmed the presence of vanadium ferrite in slag samples treated at 1773 K in an argon atmosphere (PO2 = 10−1–10−2 Pa) while no solid was noted in samples treated in air. Results were discussed based on thermodynamic consistency.