The cobalt(III)-catalyzed C(sp3)-H bond alkylation of 8-methyl quinoline with maleimides is reported. In contrast to the rhodium-catalyzed method, in the current cobalt-catalyzed method, a catalytic amount of acid is used, and importantly, it is also applicable to secondary C(sp3)-H bond alkylation. The developed methodology is applicable for N-alkyl- and N-aryl-substituted maleimides and unsubstituted maleimides, and it also tolerates the variety of functional groups on the 8-methyl quinoline moiety. Atom-economy and high regioselectivity with good to excellent yields of the alkylated products under mild reaction conditions are important features of this method.