Abstract: To achieve effective and controllable modulation of the electrical performance of tungsten diselenide field-effect transistors (WSe₂ FETs), ultraviolet-ozone (UVO) treatment was employed to modify the surface of mechanically exfoliated WSe₂ flakes and their corresponding devices. Compared with untreated samples and those subjected to oxygen plasma treatment, no obvious changes in surface morphology or material thickness were observed after UVO treatment, indicating that this method introduces negligible physical damage to WSe₂. Results from Kelvin probe force microscopy (KPFM) and electrical characterization indicate that UVO treatment effectively reduces the surface potential and increases the work function of WSe₂, resulting in a pronounced shift of the transistor threshold voltage toward zero gate bias. Benefiting from these modifications, the carrier mobility of the devices is significantly enhanced from 1.37 cm2·V⁻¹·s⁻¹ to 2.61 cm2·V⁻¹·s⁻¹. These results demonstrate that mild UVO surface modification provides an effective and facile post-treatment strategy to improve the electrical performance of WSe₂ FETs while preserving the structural integrity of the material, offering a novel approach for post-treatment processing of high-performance two-dimensional electronic devices.