An iron-catalyzed, peroxide-mediated cross-dehydrogenative coupling between 8-amidoquinolines and cycloalkanes has been developed for the site-selective alkylation of the quinoline nucleus at the C5 position. The reaction tolerates various substituted N-(quinolin8-yl)benzamides and N-(quinolin-8-yl)alkylamides, affording the corresponding C5-alkylation products in good yields. On the basis of control experiments, a reaction mechanism involving the addition of an alkyl radical to an iron-chelated intermediate is proposed.