The increased need for underwater robotic systems for exploration of underwater resources has resulted in the development of advanced control systems and technologies to overcome the challenging issues of underwater navigation and control. Developing efficient control schemes for underwater robots to maneuver in the constrained environments, overcoming the external disturbances, has been a real challenge to researchers. In this paper, we present an attitude controller for flatfish shaped underwater vehicle as an inner loop controller for trajectory control. Here the vehicle is assumed to be positive buoyant and the pitch angle variations are significant to affect the controller. The controller is designed using robust PID controller scheme and allows easy tuning of the controller, considering nominal performance and robustness as control specifications. The stability of the vehicle is also discussed. Finally, certain numerical studies are also presented to better illustrate the controller behaviour. © 2008 IEEE.