Herein, we report Ru(II)-catalyzed C–H/N–H bond functionalization of N-chlorobenzamides with 1,3-diynes via regioselective (4 + 2) annulation for the synthesis of isoquinolones under redox-neutral conditions at room temperature. This represents the first example of C–H functionalization of N-chlorobenzamides using an inexpensive and commercially available [Ru(p-cymene)Cl2]2 catalyst. The reaction is operationally simple, works in the absence of any silver additives, and is also applicable to a broad range of substrates with good functional group tolerance. The synthetic utility of the isoquinolone is demonstrated for the synthesis of bis-heterocycles consisting of isoquinolone–pyrrole and isoquinolone–isocoumarin scaffolds.