Abstract In this work, a novel biporous spiral woven mesh wick is developed to enhance the thermal performance of an ultra-thin flattened heat pipe for cooling high heat flux electronic devices. The biporous wick with different sized pores is hybrid woven using 0.05 and 0.04 mm diameter copper wires in every strand. Three different structures are designed to study the effect of the characteristic parameters of the wick on the thermal performance of the ultra-thin flattened heat pipe. The working fluid flow characteristics of the wick are analyzed theoretically. The capillary rate-of-rise experiment with deionized water using the infrared camera method is carried out to characterize the capillary performance of the wick. The thermal performance of the ultra-thin flattened heat pipe is experimentally investigated. The results indicate that the biporous wick combines the advantages of high permeability due to the large pores and large capillary force due to the small pores. The optimal biporous wick has 22% fewer copper wires than the monoporous wick, but the maximum heat transport capacity of the ultra-thin flattened heat pipe is able to approach 24 W, which realizes the demands of both low production cost and high thermal performance using the biporous wick.