Sinner moved into the last four in emphatic style on Wednesday, beating Czech Tomas Machac 6-4, 6-2 before Medvedev overcame a stern test against Chilean Nicolas Jarry before emerging with a 6-2, 7-6(7) win.
Italy's Sinner, who rallied from two sets down to beat Medvedev and claim his first Grand Slam title at the Australian Open, will play in his fourth semi of the season after dealing with lively Machac in 91 minutes.
Sinner broke the opening game serve from the Czech but Machac responded immediately to make it 1-1.
The crowd were on their feet to appreciate some brilliant defensive play from Sinner who eventually took charge of the set, breaking to go 4-3 up and then closing out.
The second set was more straightforward with Sinner breaking in the third game and never looking back.
Despite the comfortable margin of the win, Sinner said Machac deserved praise for his energetic and aggressive performance.
"He has an incredible talent. He is super fast, also physically he is in great shape," said the world number three.
"I didn't know exactly what to expect today. The first games I was looking a little bit at what kind of tactics could work or not," he added.
"I played good, especially in the important moments of the match, which makes it... the scoreboard, you see the score, but it's sometimes lying. Today was a little bit like that," said Sinner.
Good atmosphere
Medvedev ran away with the first set against Jarry, who was slow out of the blocks.
But the second set was a different story with the Chilean, roared on by heavily Latin American crowd, finding his big serve.
The pair were inseparable, with plenty of entertaining rallies, until the tiebreaker.
Medvedev missed a chance to win the match at 6-5 up when he came to the net for a routine conversion on match point but found the net - prompting a huge roar from the Chilean fans.
A thumping ace from Jarry made it 7-7 but it was followed with a poor effort which flew long and then on the third match point Medvedev wrapped up the win.
"In the first set I feel like I was playing good level, but nothing extra and it was enough to win, so I was happy about it," said Medvedev.
"Then he managed to play much better. It was tough rallies, tough points, he served better and yeah, it was a matter of a few points on the tiebreak like it is sometimes in tennis," he said.
The Russian appeared to enjoy the extra spice provided by the Chilean fans in the stadium.
"To be honest I was ready for it and I was expecting worse, when I say worse (I mean) more cheering fans supporting him.
"It was a pretty good atmosphere, you know even many times the referee was saying like players are ready, but I was like I don't care, it's actually not too bad, I've seen worse," he said.
Medvedev said he is looking forward to resuming battle with Sinner after his five-set loss in Melbourne.
"I won the first two sets - which would be enough in Miami," he quipped.
"But for sure this match is going to be different. I am sure he will adapt again and I am going to talk to my team and see what I can do better.
"I'm going to go out there, 100% ready to win and to make his life tough," said the Russian.
