Unmanned Aerial Vehicle (UAV) technology is developed as a multi-purpose aircraft system. It has several applications in many fields as: military, agriculture, surveillance and others. Since rotorcraft vehicles are generally unstable, an active attitude stabilization controller becomes an important part of the UAV systems. This paper introduces the design of an optimal PID controller to improve attitude stabilization of a four rotor vertical take-off and landing (VTOL) UAV known as qaudrotor aircraft. The proposed controller utilizes the Differential Evolution (DE) optimization algorithm to tune the parameters of the classical P11) controller. Comparison is made with the tuned PID controller based on Ziegler-Nichols tuning method, the Fuzzy PID controller (based on the expert experience to tind the optimal range arid the shape of the fuzzy membership functions) and the tuned PID controller based on genetic algorithm. The results show the superiority of the proposed controller. Simulation results are obtained using MATLAI3 program. The results are assessed in terms of dine domain factors of the quadrotor response such as overshoot, rise time, settling time and steady state error.