Ancelotti is hoping to finish his first season as Bayern coach with the league and cup double.
Both Bayern and Dortmund had their Champions League campaigns ended last week by Real Madrid and Monaco respectively in the quarter-finals, but they meet at the Allianz Arena for a place in Berlin's cup final on May 27.
Bayern are runway leaders in the German league and had been hoping for a place in the Champions League's semi-finals before a Cristiano Ronaldo-led Real thwarted their ambitions.
As compensation, Ancelotti is hoping to finish his first season as Bayern coach with the league and cup double.
However, first Dortmund must be overcome in a repeat of last year's final which Bayern won 4-3 on penalties after a goalless draw in Berlin.
"Now we want to spoil Bayern's season a little bit more," quipped Tuchel after Dortmund's 3-2 comeback win at Moechengladbach on Saturday to go third in Germany's top flight.
The victory came the day after police arrested a suspect for the April 11 bomb attack on the Dortmund team bus which left defender Marc Bartra needing wrist surgery.
"The victory put the wind in our sails and gives confidence for Wednesday," said Dortmund's director of sport Michael Zorc after Raphael Guerreiro's late header sealed the win in Gladbach.
"I'm proud of the character of this team."
While Dortmund picked up a morale-boosting victory, Bayern had to twice come from behind as they laboured to a 2-2 draw at home to relegation-threatened Mainz.
"Of course, the game against Real is still bothering us, even if it shouldn't. We're professionals, but we're also human," said Bayern's stand-in captain Thomas Mueller.
"As well as the league title, reaching the Berlin final is our biggest goal, so that means, puff out your chest and show that we deserve to be there!"
However, Bayern are winless in their last four games and picked up their only victory in their last six games, when they romped to a 4-1 win over Dortmund in the league three weeks ago.
Bayern's top-scorer Robert Lewandowski scored twice in the thumping home win, but Dortmund have Marco Reus back and the Germany winger has scored in each of his three games after six weeks sidelined by a hamstring injury.
Reus is predicting a different type of game when the teams meet again at the Allianz Arena.
"It will be totally different, I see our chance as 50-50. We have a lot of self-confidence in the tank after our win in Gladbach," said Reus.
Both teams have injury concerns.
Bayern are already without Germany's goalkeeper Manuel Neuer, who has a foot fracture, for the rest of the season and Sven Ulreich will again deputise.
Austria defender David Alaba is doubtful with a knee injury having limped off early in Saturday's draw against Mainz, but Ancelotti hopes to have centre-backs Jerome Boateng (groin) and Mats Hummels (ankle) fit again.
Tuchel is hoping defender Sokratis Papastathopoulos overcomes a leg knock, while Turkey midfielder Nuri Sahin is out with suspected torn ankle ligaments.
On Tuesday, Borussia Moenchengladbach host Eintracht Frankfurt in the other semi with both teams chasing their first final appearance in more than a decade.
German Cup semi-finals (1845 GMT)
Borussia Moenchengladbach v Eintracht Frankfurt
Bayern Munich v Borussia Dortmund