Tractor-trailer wheeled platforms are recognized as articulated robotic systems which consist of a frontrunner active mobile platform (known as tractor) that pulls one or more passive platforms (known as trailers). Regarding to their novel features such as maximum load carrying capacity and minimum energy consumption, this category of mobile platforms is widely employed for conveying purposes and transportation. The presented article deals with path tracking optimization of the tractor-trailer platform using the indirect method of the optimal control. First, nonlinear motion relations of the modular platform are obtained considering kinematic constraints and inertia characteristics of the wheels. Then, the obtained dynamic equations are considered as constraints of the optimal problem, and as a result an appropriate objective criterion is determined for the optimal trajectory tracking. In the following, a proper solution for the optimal problem is developed and accordingly some simulations are presented. In view of the wheels dynamics, the obtained results reveal competency and applicability of the proposed procedure for the optimal tracking of the tractor-trailer wheeled mobile platforms.