Youzhny, 31, is bidding to become the first Russian champion at the Swiss Open after beating Romania’s Victor Hanescu 6-3 6-3.
Dutchman Haase overcame Feliciano Lopez of Spain 4-6 6-1 6-4 in an hour and 48 minutes.
"I served well today and I was fighting a lot," said Haase.
"I was broken early in the first set and that’s the worst thing that can happen to you against Feliciano.
“But I managed to fight back and I’m very happy to be in the final."
Youzhny has beaten Haase in all four of their previous encounters.
"It will be a difficult match," said Haase. "His game doesn't suit me. He's a great player with a lot of experience."
In Croatia, Fognini won 6-0 3-6 7-6(3) against France’s Gael Monfils, who came from 5-0 down in the decider and saved two match points himself before going out on a tie-break.
Fognini will play Spain’s Tommy Robredo in the Umag final after he triumphed over Italian Andreas Seppi 6-3 2-6 6-4.
- Sports & Recreation
- Feliciano Lopez
- Victor Hanescu