This study presents the modeling, trajectory generation, and control of a four mecanum-wheeled mobile robot using the Robot Operating System (ROS) integrated with the Gazebo simulation environment. Leveraging both kinematic and dynamic models, cubic polynomial trajectory generation was applied to plan robot motion, while a Proportional–Integral–Derivative (PID) controller was employed to ensure accurate tracking. The robot’s kinematic parameters were defined through Unified Robot Description Format (URDF) modeling, and velocity commands were transmitted to each wheel while feedback was obtained from odometry data. Simulation experiments were conducted for linear and diagonal trajectories, and the influence of PID parameters on position and velocity errors was analyzed. Results demonstrate that carefully tuned PID gains significantly reduce tracking error, ensuring smooth and stable motion along the desired path. The proposed framework highlights the potential of combining ROS and Gazebo as a cost-effective and flexible platform for developing, testing, and refining control strategies prior to real-world implementation.