We demonstrate fully inkjet-printed graphene-gated organic electrochemical transistors (OECTs) on polymeric foil for the enzymatic-based biosensing of glucose. The graphene-gated transistors exhibit better linearity, repeatability, and sensitivity than the printed silver-gated devices studied in this work and other types of printed devices previously reported in the literature. Their limit of detection is 100 nM with a normalized sensitivity of 20%/dec in the linear range of 30–5000 μM glucose concentrations, hence comparable with state-of-the-art OECT devices made by lithography processes on rigid substrates and with complex multilayer gates. Electrochemical impedance spectroscopy analysis shows that the improved sensitivity of the graphene-gated devices is related to a significant decrease of the charge-transfer resistance at the graphene electrode–electrolyte interface in the presence of glucose. The optimized sensing method and device configuration are also extended to the detection of the metabolite lactate. This study enables the development of fully printed high-performance enzymatic OECTs with graphene-sensing gates for multimetabolite sensing.