Nishikori got a near three-year-old monkey off his back with the defeat of Daniil Medvedev at Pat Rafter Arena, the title snapping a run of nine finals losses since his last tour win in February 2016.
Tsonga, 33, overcame the seventh-seeded rising Australian star 6-4 7-6 (7-2) in a high-quality contest to set up a meeting with Andy Murray's conqueror Daniil Medvedev on Saturday.
Tsonga, on the comeback from knee surgery that saw him miss seven months of last year's tour, couldn't touch the Russian in the second set as the match wrapped up in 84 minutes. The Frenchman hit a backhand victor down the line to take his second break and a 5-4 first half lead, before serving out to love to clinch the opener.
Medvedev will next play 2008 Australian Open finalist Jo-Wilfried Tsonga, who beat Alex de Minaur 6-4, 7-6 (2).
Canadian Raonic showed the stronger serving game in the first set when he slammed down 12 of his 29 aces.
Hoping to extend his first-tournament appearance, Medvedev broke Raonic's serve at the beginning of the second set and sent on to draw level.
Last year's finalist Nishikori, who prevailed 6-4 3-6 6-2, won 70 percent of points on his first serve and converted five out of 15 break point opportunities to snap a nine-match losing streak in finals.
"I'm happy to go into Melbourne, one of my favourite tournaments there", he said.
Medvedev rose to No. 16 in the rankings after winning three ATP titles previous year, including the Sydney International before being a second-round casualty in Melbourne. "I've never had a match like this, but I'm happy I'm back in the semis", Pliskova, who fired 14 aces and 27 winners, said.
"Nothing better than this today".
Eying his 12th title in his 26th career final, Nishikori will take on the victor of the second semifinal clash pitting Frenchman Jo-Wilfried Tsonga against Daniil Medvedev of Russian Federation.
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