Djokovic, who downed Mardy Fish in last year's Toronto finale, breezed past Australian Bernard Tomic, 6-2, 6-3 in a second-round match.
The world No. 2 now goes on to face American Sam Querrey, who bested 13th-seed Kei Nishikori of Japan 6-2, 6-3 earlier Wednesday.
Meanwhile, second-seeded Murray continued the momentum he built the London games, taking his seventh straight match overall by downing Italian qualifier Flavio Cipolla 6-1, 6-3.
His next opponent is 16th-seeded Canadian Milos Raonic.
An upset overtook sixth-seeded former U.S. Open champion Juan Martin del Potro, however. He fell to the Czech Republic's Radek Stepanek 6-4, 7-6 (7-5) on Day 3.
France's Jeremy Chardy pulled off another surprise, dismissing third-seeded fellow Frenchman Jo-Wilfried Tsonga 6-4, 7-6 (7-4).
Other winners Wednesday included fourth-seeded Czech Tomas Berdych, fifth-seeded Serb Janko Tipsarevic, Germany's Tommy Haas, 10th-seeded Croat Marin Cilic and 12th-seeded German Philipp Kohlschreiber.
France's Richard Gasquet and Spaniard Marcel Granollers also pulled out Day 3 victories.