Flexible organic field-effect transistors with high electrical stability upon bending are demonstrated on indium tin oxide coated polyethylene terephthalate substrates with TIPS-Pentacene semiconductor crystals formed by drop casting on a hybrid gate dielectric consisting hafnium dioxide grown by atomic layer deposition and spin coated poly(4-vinylphenol). Fabricated devices exhibited excellent p-channel characteristics with field-effect mobility up to 0.12cm2/Vs with high current on/off ratio >104 and low threshold voltage of -0.2 V. Device performance was slightly affected by mechanical strain applied by bending for 5 min with radius varying from 12.5 mm to as low as 5.0 mm; and a high stability in performance was demonstrated upon applying constant tensile strain for more than 48 h at bending radius of 5.0 mm. It was found that strain induced changes in the device performance primarily occur due to increase in dielectric surface roughness; and the semiconductor-dielectric interface uniformity is influenced more with magnitude of strain rather than its duration. © 2016 Elsevier B.V. All rights reserved.