In the study of vehicle dynamics, there are some contradictions between experimental results and results obtained from linear models. The nonlinear characteristics of vehicle components are the source of these contradictions in linear models. In practice an automobile is a nonlinear system because it consists of suspensions, tires and other components that have nonlinear properties. Owing to the existence of nonlinear factor, the vehicle exhibit complex phenomena such as jumps, bifurcation and chaotic vibrations when running on bumpy road, which are quite harmful to the stabilization of a vehicle. Thus, study of these nonlinear behaviors in studying of the dynamic response of the vehicle is necessary. Hence, the chaotic vibration analysis of nonlinear full-vehicle model with passengers is investigated. The vehicle system is modeled as full nonlinear seven degrees of freedom with an additional one-degree of freedom for each passenger. Four passengers are added sequentially to the vehicle that produces eight, nine, ten and eleven degrees of freedom models, respectively. The nonlinearities of the system are due to the nonlinear springs and dampers that are used in the suspension and tires. Roughness of the road surface is considered as sinusoidal waveforms with time delay for tires. The governing differential equations are extracted by Newton-Euler laws and are solved numerically via forth-order Runge-Kutta method in. The dynamic behavior of the system is investigated by special nonlinear techniques such as time series, phase plane portrait, bifurcation diagrams, power spectrum, Poincaré section and maximum Lyapunov exponents. Initially, the effect of passengers on the chaotic vibration of vehicle is studied. The comparison of the results that obtained from the of the vehicle models with passengers and those from the vehicle without passenger model, shows that the passenger has great influence on the dynamical behavior of the system, which cannot be ignored. Then, the effect of road roughness model on nonlinear dynamic behavior of a full vehicle model was examined. For this purpose, the rectangular and triangular waveforms were used to describe roughness of the surface and were compared with the sine wave. The results obtained from of the bifurcation diagrams in rectangular and triangular roughness waveforms shows the difference irregular regions than sine wave. Finally, the effect of system parameters such as damping and stiffness coefficients of suspension and seats on chaos was studied and discussed in detail. Results show choosing the appropriate regions of the system parameters can be lead to exit the system from chaotic behavior. Keywords Full-vehicle model, Chaotic vibration, Dynamic behavior, Poincaré section, Lyapunov exponents.