Two-phase thermal management systems such as heat pipes and vapor chambers offer high heat flux cooling performance in modern electronics and spacecrafts. However, the cooling performance is limited by poor wickability, i.e., ratio of permeability to capillary pumping capability, . In this study, we examine the enhanced wickability using bi-particle-size, sintered-particle wicks. The bi-particle-size wicks are sintered particle wicks having two different particle sizes (200/60, 200/100, 350/60, 550/60 μm) with two different particle weight ratios (75:25 and 50:50 wt%), and the wickability are characterized using a rate-of-rise method with FC-72 as a working fluid. It is found that the single-layer 200/100 μm (50:50 wt%) bi-particle-size wick enhances the wickability by 27% and 35%, compared to that of 200 and 60 μm uniform particle wick, respectively. This enhancement is due to the increased permeability from the large particle size and the reduced effective capillary meniscus radius from the small particles. This work provides an insight into advanced wick designs for high heat flux two-phase cooling systems.