Hygrothermal diffusion behavior of bismaleimide resin prepared by two different curing schedules is studied. The Langmuir model is employed to describe the non-Fickian diffusion behavior observed at two different hygrothermal conditioning temperatures. Dynamic mechanical analysis, attenuated-total-reflectance Fourier transform infrared spectroscopy and swelling experiments were conducted to investigate the nature of the diffusion process. The experimental findings reveal that both hydrogen bonding and the nature of the network architecture strongly affect the hygrothermal diffusion behavior of the bismaleimide resin. The possible diffusion mechanisms accounted for such a non-Fickian diffusion behavior are discussed.