In the development of disease diagnoses, rapid responses to and accurate selectivity for target analytes are critical aspects. As one diagnostic approach, biosensors with high sensitivity and selectivity are investigated to detect disorder factors (e.g., endocrine disruptors and cancer oncoproteins). In this report, we demonstrate an aptamer-functionalized multidimensional hybrid conducting-polymer (3-carboxylated polypyrrole) plate (A_MHCPP) based field-effect transistor (FET) sensor to detect a platelet-derived growth factor (PDGF-BB). The multidimensional hybrid conducting-polymer plates (MHCPPs) are formed on the graphene surface by using electrodeposition and vapor deposition polymerization (VDP) steps. The amine-functionalized PDGF-B binding aptamers are then immobilized on the carboxylated polypyrrole surface by means of covalent bond formation (-CONH). The prepared FET sensors present high sensing ability toward PDGF-BB - as low as 1.78 fM among interfering biomolecules at room temperature.