A boryl radical-promoted dehydroxylative alkylation of 3-hydroxy-oxindole derivatives is achieved. The reaction starts from addition of 4-dimethylaminopyridine (DMAP)-boryl radical to the amide carbonyl oxygen atom, which induces a spin-center shift process to promote the C-O bond cleavage. The elimination of a hydroxide anion from a free hydroxy group is also accomplished. Capture of the generated carbon radical with alkenes furnishes a variety of C-3 alkylated oxindoles. This method features a simple operation and broad substrate scope.