Psoriasis is a chronic inflammatory skin disease that significantly affects the quality of life of patients. Photodynamic therapy is effective in treating psoriasis; however, existing light sources, such as lasers and light-emitting diodes (LEDs), have limitations in terms of flexibility, uniformity of light irradiation, and patient convenience. In this study, a high-power ultraflexible organic LED (OLED) patch is fabricated on a PET adhesive film, resulting in a high output of 60 mW cm<sup>-2</sup> at 7.5 V. Based on high-performance encapsulation technology, the OLED patch achieved a lifetime of 177 h and no performance change after bending for 10 000 times for a radius of 2 mm at 35 mW cm<sup>-2</sup>. Finally, photodynamic therapy is performed in a psoriasis mouse model using an OLED for the first time, and the effect is confirmed through a cross-sectional analysis of the mouse skin, in which the thickness of the diseased area is reduced by 66% compared with the control group.