Polydopamine (PDA) is widely used to modify the membrane surface to increase the hydrophilicity with the goal of producing a low fouling membrane. However, current methods of PDA modification require alkali conditions and relatively long reaction times. Herein, we introduced the use of UV irradiation during the PDA modification of the membrane surface. The effects of UV irradiation on the characteristics of the synthesized PDA and the performance of the resulting membrane were evaluated. The PDA was rapidly synthesized in DI water, providing a significant increase in hydrophilicity and a reduction in surface roughness of the polyamide reverse osmosis (RO) membranes. The PDA-modified RO membranes exhibited excellent antifouling behavior upon exposure to alginate while maintaining good water permeability and salt rejection. The use of UV allowed the PDA modification to be conducted in DI water in less than 30 min, a significant improvement compared to current methods.