Abstract: Molecular dynamics simulations are utilized to systematically investigate the effects of wettability on capillary imbibition process at the nanoscale. We consider two sets of scenarios. In the first set, the two sidewalls of a nanochannel have the same wettability. We find that the capillary imbibition rate increases with the hydrophilicity of capillary and that the imbibition dynamics deviates from the Lucas-Washburn theory at the early stage but agrees with it at the late stage. In the second set where the two sidewalls have different wetting conditions, the liquid-vapor interface oscillates, and there exists a difference between the capillary height of the two sidewalls. The amplitude of the liquid-vapor interface oscillation and the capillary height difference increase with the wettability contrast between the two sidewalls. We determine the critical condition for the occurrence of capillary imbibition in the nanochannel with inhomogeneous wettability, and propose a method to estimate the evolution of the capillary height. Our findings deepen the understanding of capillary dynamics at the nanoscale and could be useful for relevant engineering applications.