Multi-site modification of sugars represents a highly promising strategy for constructing bioactive molecules in glycosciences. However, the modular assembly of diversifiable sugar architectures from readily available precursors remains a considerable challenge. Here, we disclosed a photoredox-catalyzed alkylarylation of glycals that achieves simultaneous diversification at the C1 and C2 positions of sugars. The reaction enables the synthesis of diverse 2-C-alkyl branched heteroaryl/aryl-C-glycosides, including unprotected ones, with excellent regio-, site-, and stereoselectivities, and is compatible with an array of (hetero)-arenes and alkyl branches bearing a variety of functional groups. The utility is demonstrated through the gram-scale synthesis and the efficient downstream modifications on the easily functionalizable C2 alkyl branches and the C1 (hetero)-arenes, as well as the identification of a 2-C-alkyl phosphate aryl-C-glycoside as a potent antitumor agent through preliminary biological evaluation. A reaction mechanism is proposed based on radical trapping and Stern–Volmer luminescence experiments. Collectively, this study developed a modular, dual-functional sugar diversification platform that facilitates simultaneous Csp3─Csp2 and Csp3─Csp3 bond formation at the saccharide skeleton, which represents an alternative strategy for the rapid construction of complex carbohydrate derivatives for drug discovery.