Abstract：Sulfur-based chiral centers play a critical role in drug discovery yet pose significant challenges in achieving precise stereochemical control. Sulfinamides, serving as versatile intermediates and chiral auxiliaries, have traditionally required multistep synthesis or auxiliary-dependent strategies. Recent advances using N-sulfinyltritylamine (TrNSO) enabled catalytic arylative additions; however, stereoselective alkylative approaches remain underdeveloped, likely due to the highly reactive alkyl radical intermediate. Herein, we report a cobalt-catalyzed reductive addition strategy for direct enantioselective C(_sp3)–S bond formation between TrNSO and unactivated alkyl halides. Leveraging an unprecedented 8-Quinox cobalt catalyst, this method delivers alkyl-substituted sulfinamides with broad substrate scope, excellent functional group tolerance, and high enantioselectivity. The protocol is further extended to a cascade addition/cyclization sequence, facilitating the efficient synthesis of enantioenriched sultims. DFT calculations reveal stereochemical control arises from selective alkyl radical addition orchestrated by the chiral cobalt catalyst.