The 22-year-old Tomic eased past the world No.24 6-3 6-4 to set-up a quarterfinals showdown with Gilles Muller.
Tomic’s strong service formed carried over into Wednesday night’s encounter, smashing eight aces and winning 75 percent of his service points.
There was no looking back for Tomic after earning a break late in the first set. He went on to steal another break on Kohlschreiber’s first service game of the second set before holding his serve to wrap up the match in 58 minutes.
“I went for my shots and did the right things and I am very happy with how I played,” Tomic said.
“I needed to do that from the start against Philipp. I’m very pleased with the way I played for sure. He’s very experienced and a quality player, that’s why he’s been for many years inside the top 20.”
The win marked Tomic’s first against the highly touted German and his third straight appearance in the Sydney International’s final eight after winning the tournament in 2013 and dropping last year’s final to Juan Martin Del Potro in straight sets.
Earlier on Wednesday, Aussie Jarmila Gajdosova saw her Sydney International run come to an end at the hands of world No.4 Andrea Petkovic 4-6 6-3 6-4.
The world No.68 put up a spirited fight in over two hours of match time after knocking out top 15 players Andrea Petkovic and Dominika Cibulkova on the way to a quarterfinals appearance.
Photo: Matt King/Getty Images.