<p>In this work, we address the problem of achieving flocking behavior in a group of nonholonomic wheeled mobile robots without using attitude measurements. Based on the cascade structure of the kinematic model of the mobile robot, we propose a dynamic controller that drives the position of each robot to a desired geometric pattern while maintaining a desired linear velocity. To overcome the problem of lack of attitude measurements, we propose an attitude observer that estimates the direction of the robot’s velocity. The interaction between robots is modeled using graph theory and the stability analysis is carried out by exploiting the properties of interconnected nonlinear systems. Experimental results on a group of four robots are provided to show the performance of the proposed control-observer algorithm.</p>