2-Methacryloyloxyethyl phosphorylcholine (MPC) polymers including hydrophobic units such as poly(MPC-co-butyl methacrylate) (PMB) and poly(MPC-co-dodecyl methacrylate) (PMD) are used as coating agents for medical devices because of their antifouling effects. In this study, the whole hydration process of MPC polymer-coated surfaces was investigated using air-injectionmediated liquid exclusion (AILE) methods in which the liquid exclusion diameter during air injection was correlated to the waterrepelling property. The prejetted and standard AILE methods showed the initial change from a dry to a wet state and the swelling behaviors of the MPC polymers, respectively. The liquid exclusion diameter of the MPC polymer-coated surfaces increased with an increase in the immersion time in various aqueous solutions such as deionized water, phosphate-buffered saline (PBS), and cell culture media. Moreover, the liquid exclusion diameter of the PMD-coated surface was larger than that of the PMB-coated one. Ellipsometry directly indicated the polymer layers swollen in water. Scanning probe microscopy (SPM) revealed that nanosized protuberances were formed in water, especially at the PMD-coated surface. The different swelling behaviors of these MPC polymercoated surfaces affected the liquid exclusion diameters. Thus, the AILE methods are a powerful tool to elucidate the hydration process in various liquid media.