Photolithographic defined films play an important role in modern optoelectronics and are crucial for the development of advanced organic thin-film transistors (OTFTs). Here, we explore a facile photoresist-free photopatterning technique for natural carbohydrates and their use as OTFT gate dielectrics. The effect of the cross-linkable chemical structure on the crosslinking chemistry and dielectric strength of the corresponding films are investigated in cinnamate-functionalized carbohydrates from monomeric (glucose) to dimeric (sucrose) to polymeric (cellulose) backbones. UV-illumination of the cinnamate esters of these carbohydrates leads to [2+2] cycloaddition and thus the formation of robust crosslinked dielectric films in the irradiated areas. Using propylene glycol monomethyl ether acetate as the solvent/developer, patterned dielectric films with micrometer size features can be readily fabricated. P- and N-type OTFTs are successfully demonstrated using unpatterned/patterned crosslinked films as the gate dielectric and pentacene and N,N’-1H, 1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) as the p- and n-channel semiconducting layers, respectively. These results demonstrate that natural-derived polymer gate dielectrics, which are soluble and patternable using bio-mass derived solvents, are promising for the realization of a more sustainable OTFT technology.