In pentacene organic field-effect transistor (OFET) devices without encapsulation, the off-state current and voltage hysteresis quickly increase during cyclic bending, due to the cracking of the pentacene layer. As a result, the doping effects caused by O(2) and H(2)O in the atmosphere exacerbate their electrical instability. In order to mitigate this aggravation of the electrical instability of unencapsulated pentacene OFETs under cyclic bending, flexible multistack hybrid encapsulation by plasma-polymerized methylcyclohexane (MCH) and atomic-layer deposited Al(2)O(3) layers is investigated. With multistack hybrid encapsulation, the electrical stabilities of the OFETs are improved significantly with a negligible change in the voltage hysteresis and stable off-state current, due to the enhanced protection of the active layers in the device from the atmosphere. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610405] All rights reserved.