Pitch control of a wind turbine is important in its designing, optimizing the generator output power, and reducing the fatigue load of its inner parts. Moreover, pitch control is applied to eliminate possible dangers due to an unpredicted increase of wind speed, and consequently, sudden increase of the output power. The most common approach is to change the rotor speed through adjusting its blades angle with applying PID controllers. Regarding irregular winds and nonlinear behavior of blades in wind turbines, designing PID controllers would be difficult. Therefore, fuzzy controllers have been used in the most recent methods. A point of note in the present study is applying Interval Type-2 Fuzzy Logic (IT2FL) in designing fuzzy controllers instead of PID controllers to work around nonlinearity of the pitch control problem. IT2FL controllers have all the benefits of Type-1 fuzzy controller, i.e. independency from the model of the studied system. In addition, IT2FL theory shows uncertainties of the parameters better than Type-1 and causes more accurate results. In comparison with previous methods, our results indicated that applying IT2FL along with the maximum number of influential parameters in regulating the wind turbine output power has made the blades to change their angle at the right time, and has resulted in proper rotor speed adjustment, and consequently, of the output power. Furthermore, results presented that the IT2FL controller in compare with PI controller has better improvement in adjustment of pitch angle, and also in control of the rotor speed and the output power to achieve rated power of the generator.