Abstract: The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO−V₂O₅, which is the predominant binary mixture involved in the vanadium recovery process. Thermal analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples. The extent of the solid reaction was derived using the preliminary quantitative phase analysis of the X-ray patterns. The results indicate that the solid reaction of the CaO−V₂O₅ mixture is strongly influenced by the reaction temperature and CaO/V₂O₅ mole ratio. The transformation of calcium vanadate involves a step-by-step reaction of CaO−V₂O₅, CaO−CaV₂O₆, and CaO−Ca₂V₂O₇ depending on the CaO/V₂O₅ mole ratio. The kinetic data of the solid reaction of the CaO−V₂O₅ (1:1) mixture followed a second-order reaction model. The activation energy (E_a) and preexponential factor (A) were determined to be 145.38 kJ/mol, and 3.67 × 10⁸ min⁻¹, respectively.