Succinyldiamide derivatives are important structural motifs in various natural products, pharmaceuticals, and functional materials. Herein, a novel, mild, and environmentally friendly method was developed for synthesizing functionalized succinyldiamides each containing a quaternary carbon center. This strategy was designed to involve photocatalytic decarboxylation of readily available oxalic monoamide using a non-precious metal photocatalyst, 4CzIPN, followed by a free-radical addition/Smiles rearrangement cascade reaction of N-aryl-N-(arylsulfonyl)acrylamides. This method was found to display several advantageous features including compatibility with many substrates, easily accessible starting materials, and operational simplicity.