Experiments were conducted to investigate the subcooled flow boiling heat transfer characteristics of binary mixtures in microchannel plates. Generally, mixtures with small more volatile component concentrations augmented the how boiling heat transfer, while those with large concentrations decreased the heat transfer as compared with the pure more volatile liquid. There existed an optimum concentration at which the flow boiling heat transfer reached a maximum value. These characteristics were found to be affected by both liquid flow velocity and amount of subcooling. The heat transfer coefficient at the onset of how boiling and in the partial nucleate boiling region was greatly influenced by liquid concentration, microchannel and plate configuration, flow velocity and amount of subcooling. However, microchannel size, flow velocity, subcooling of the mixture, and liquid concentration had no significant effect on the heat transfer coefficient in the fully nucleate boiling regime. The level of augmentation induced by increasing the number of channels diminished as size decreased.