This paper aims to propose a nonlinear attitude controller for a drone system controlled by the control momentum gyros (CMGs). The dynamic modeling and the control mechanism of the considering system are ﬁrst investigated. After that, based on the assumption of the timescale separation, the proposed controller is designed using the feedback linearization methodology. To make the resultant controller follow the three-loop structure, speciﬁc forms of the desired error dynamics are utilized in the design step. The characteristics of the proposed method are investigated through numerical simulations. The results show that the proposed controller can provide a good tracking performance against model uncertainties as well as model nonlinearities.