This study reports the first photobiocatalytic oxidative cross-coupling process for the stereoselective synthesis of non-canonical amino acids (ncAAs) using a cooperative system of engineered pyridoxal biocatalysts, photoredox catalysts, and an oxidizing agent. The process enables the formation of C(sp³)-C(sp³) bonds with excellent stereocontrol, allowing the α-C-H functionalization of glycine and α-branched amino acid substrates via a novel radical mechanism. The cooperative catalysis repurposes a family of pyridoxal-5'-phosphate (PLP)-dependent enzymes, such as threonine aldolases, to catalyze the α-functionalization of amino acids, leading to a range of valuable α-tri- and tetrasubstituted ncAAs with up to two contiguous stereocentres. Directed evolution of pyridoxal radical enzymes allows the coupling of a broad spectrum of primary and secondary radical precursors, including benzyl, allyl, and alkylboron reagents, in an enantio- and diastereocontrolled fashion. The design and development of novel asymmetric intermolecular radical reactions are at the forefront of free radical chemistry, with this study demonstrating the potential of cooperative photoredox–pyridoxal biocatalysis to enable new oxidative coupling strategies. The reaction mechanism involves the generation of a benzyl radical, which undergoes stereoselective addition to the α-carbon of a quinonoid intermediate, followed by a single-electron oxidation to form a new external aldimine and regenerate the catalysts. The study also highlights the broad substrate scope of the reaction, including various substituted benzylboronates and allylboronates, and demonstrates the scalability of the process. The results show that the cooperative system enables the stereoselective synthesis of valuable ncAAs with high enantio- and diastereocontrol, and the potential for further directed evolution to expand the range of organoboron reagents that can be used. The study also provides insights into the reaction mechanism, including the role of the PLP enzyme in the α-deprotonation of the external aldimine and the formation of the quinonoid intermediate. The findings demonstrate the potential of photobiocatalysis to enable new strategies for the stereoselective synthesis of complex molecules.This study reports the first photobiocatalytic oxidative cross-coupling process for the stereoselective synthesis of non-canonical amino acids (ncAAs) using a cooperative system of engineered pyridoxal biocatalysts, photoredox catalysts, and an oxidizing agent. The process enables the formation of C(sp³)-C(sp³) bonds with excellent stereocontrol, allowing the α-C-H functionalization of glycine and α-branched amino acid substrates via a novel radical mechanism. The cooperative catalysis repurposes a family of pyridoxal-5'-phosphate (PLP)-dependent enzymes, such as threonine aldolases, to catalyze the α-functionalization of amino acids, leading to a range of valuable α-tri- and tetrasubstituted ncAAs with up to two contiguous stereocentres. Directed evolution of pyridoxal radical enzymes allows the coupling of a broad spectrum of primary and secondary radical precursors, including benzyl, allyl, and alkylboron reagents, in an enantio- and diastereocontrolled fashion. The design and development of novel asymmetric intermolecular radical reactions are at the forefront of free radical chemistry, with this study demonstrating the potential of cooperative photoredox–pyridoxal biocatalysis to enable new oxidative coupling strategies. The reaction mechanism involves the generation of a benzyl radical, which undergoes stereoselective addition to the α-carbon of a quinonoid intermediate, followed by a single-electron oxidation to form a new external aldimine and regenerate the catalysts. The study also highlights the broad substrate scope of the reaction, including various substituted benzylboronates and allylboronates, and demonstrates the scalability of the process. The results show that the cooperative system enables the stereoselective synthesis of valuable ncAAs with high enantio- and diastereocontrol, and the potential for further directed evolution to expand the range of organoboron reagents that can be used. The study also provides insights into the reaction mechanism, including the role of the PLP enzyme in the α-deprotonation of the external aldimine and the formation of the quinonoid intermediate. The findings demonstrate the potential of photobiocatalysis to enable new strategies for the stereoselective synthesis of complex molecules.