The Swizterland player avenged his US Open quarter-final defeat to Nishikori in style with a comprehensive 6-3 6-4 7-6 victory to charge into the final four of the tournament.
The fourth-seeded has worked his way slowly into the year's first Grand Slam but put laid down his marker on a sun-drenched Rod Laver Arena, dominating Nishikori with power and compiling an detailed highlights reel of winners.
Wawrinka's backhand was particularly effective, picking off his opponent from all points of the court, but Wawrinka was also impressive rushing to the net, a relatively new weapon in his arsenal.
However, he did make hard work of the tiebreak in third set, blowing five match points after storming to a 6-1 lead, but closed it out on the sixth with an ace in just over two hours to set up a semi-final with the winner of top seed Novak Djokovic and Milos Raonic.
After the match, Wawrinka told reporters: "I am still nervous about that tiebreak, I was a bit defensive, it's never easy, you have to go for it and I'm happy to get through.
"It's going to be a tough one in the semi, but I'm playing well so I am happy to be back again to be playing in the semi-final. I will watch tonight's match and then practice tomorrow."