Regioselective C-H functionalization on quinolines is of high interest to lead to value-added products. Herein, we describe the development of Ru-catalyzed deoxygenative regioselective C8 arylation of quinoline N-oxides with arylboronic esters. Mechanistic studies revealed that it proceeds in a tandem process of arylation and then deoxygenation, wherein both steps were found to be catalytic with the ruthenium species.