— In this paper a new leader-follower formation of nonholonomic mobile robots is studied. The follower is a car-like vehicle and the leader is a tractor pulling a trailer. The leader moves along assigned trajectories and the follower is to maintain a desired distance and orientation to the trailer. A sliding mode control scheme is proposed for asymptotically stabilizing the vehicles to a time-varying desired formation. The attitude angles of the follower and the tractor are estimated via global exponential observers based on the invariant manifold technique. Simulation experiments illustrate the theory and show the effectiveness of the proposed formation controller and nonlinear observers.