The transition-metal-promoted C-H activation has become an efficient as well as atom-economic methodology for the synthesis of a wide array of organic molecules, but the cost of the metal catalyst and selectivity remain the major challenges. Herein, the first [Cl2Ru(p-cymene)]2-catalyzed direct monoarylation of unactivated C(sp3)-H bonds of 8-methyl quinolines with arylboronic acids to synthesize diarylmethane compounds is presented. The transformation shows a broad substrate scope with high chemoselectivity for the synthesis of 8-benzyl quinolines. In the preliminary mechanistic studies, control experiments, deuterium labeling experiments, and kinetic studies have been performed.