Alkylated benzosulfonamides are compounds of high importance in organic synthesis, including the production of pharmaceuticals, agrochemicals, and plasticizers. We report the iron-catalyzed C(sp2)-C(sp3) cross-coupling of chlorobenzosulfonamides with alkyl Grignard reagents under mild and sustainable conditions. Electronically and sterically varied benzosulfonamides as well as challenging alkyl organometallics containing β-hydrogen afford alkylated benzosulfonamides in high to excellent yields. Sulfonamide represents the most reactive activating group for iron-catalyzed cross-coupling. The process affords alkylated benzenesulfonamides poised for medicinal chemistry applications and traceless reductive cleavage.