This study investigates the influence of annealing temperature (200–500 °C) and atmosphere (air vs. oxygen) on the properties of VO2 thin films deposited by RF magnetron sputtering. XRD analysis revealed a mixed-phase composition (VO2/V2O5), with oxygen annealing promoting preferential VO2growth at higher temperatures. AFM demonstrated that oxygen atmosphere significantly reduced surface roughness (41.43 nm at 500 °C) compared to air annealing (150.6 nm), while SEM-EDX confirmed a linear rise in oxygen content with temperature. The results highlight oxygen annealing as a superior approach for achieving phase-pure VO2 with enhanced morphological stability, critical for thermochromic applications.