Modern clinical chemistry research has revealed a significant demand for materials that can be used in biomarker screening. Accordingly, we have developed a simple enzyme-free electrochemical sensor for the detection of L-Tyrosine (L-Tyr) based on the enhanced electrocatalytic activity of a novel ternary nanocomposite material. The nanocomposite was prepared by decorating zirconium dioxide (ZrO 2 ) nanoparticles onto a polyaniline−graphene oxide composite, which was subsequently named as PGZ, incorporating the first letters from polyaniline, graphene oxide, and zirconium dioxide. Electrodes modified with the new material could selectively detect L-Tyr at physiological pH in the presence of common interfering biomolecules. Differential pulse voltammetric studies with the sensor showed a satisfactory linear response for L-Tyr in the range of 100 nM−250 μM and a very low detection limit of 2 nM. The modified electrode was conveniently fabricated, which displayed excellent sensitivity, selectivity, and reproducibility. It could also successfully detect the amino acid in human blood samples. The miniaturization of electrochemical assembly was performed by modifying the screenprinted electrode (SPE) with the PGZ composite, which may be further extended to the manufacture of devices for the highly sensitive and selective detection of L-Tyr in various biological samples.