Biomaterials have been attracting attention as a useful building block for biocompatible and bioresorbable electronics due to its non-toxic property and solution processabillity. In this work, we report the integration of biocompatible keratin from human hair as dielectric layer for organic thin-film transistors (TFTs), with high performance, flexibility and transient property. The keratin dielectric layer exhibited a high capacitance value above 1.27 µF/cm2 at 20 Hz due to the formation of electrical double layer. Fully solution processable TFTs based on p-channel poly[4-(4,4-dihexadecyl-4H-cyclopenta[1,2-b:5,4-b]dithiophen-2-yl)- alt[1,2,5]thiadiazolo[3,4-c]-pyridine] (PCDTPT) and keratin dielectric exhibited high electrical property with a saturation field-effect mobility of 0.35 cm2 V-1 s-1 at a low gate bias of -2 V. We also successfully demonstrate flexible TFTs which exhibited good mechanical flexibility and electrical stability under bending strain. An artificial electronic synaptic PCDTPT/Keratin transistor was also realized and exhibited high-performance synaptic memory effects via simple operation of proton conduction in keratin. An added functionality of using keratin as a substrate was also presented, where similar PCDTPT TFTs with keratin dielectric were built on top of keratin substrate. Finally, we observed that our prepared devices can be degraded in ammonium hydroxide solution, establishing the feasibility of keratin layer as various components of transient electrical devices including as a substrate and dielectric layer.