In this work, a model for characterizing the ballasted track–vehicle interaction is presented. The vehicle is modeled as a multirigid-body system consisting of a car body, two bogie frames, and four wheelsets, and the track is modeled by finite elements including the rail, the sleeper, and the track bed. All bodies are connected by spring–dashpot elements. With novelty, the geometric nonlinearity of curved rail beam and mechanical nonlinearity of ballasted bed lateral resistance have been fully considered. Besides, numerical solution procedures including iteration and increment have also been developed to accurately clarify the dynamic nonlinear performance of vehicle–track systems. Apart from model validations in statics and dynamics, the influence of track nonlinearity and curved track radius on vehicle–track dynamic performance has been revealed in detail.