The Russian will battle another German, Nicolas Kiefer, in the men's championship Sunday.
On the women's side, Elena Dementieva will face Yugoslavia's Jelena Dokic in the final after winning her all-Russian encounter with wild card Anastasia Myskina.
Kafelnikov, gunning for his 24th career ATP title, took the opening four games of the match and never looked back. All week, the 27-year-old has pointed to his compatriots' support as the reason for his strong performances.
"It is one of the best matches I have played here," said Kafelnikov, who improved to 5-1 lifetime against Haas. "The situation was difficult for me because I was under extreme pressure from myself and the crowd. The only thing I could give them today was the victory."
Haas, who captured the AAPT Championships and Hamlet Cup titles earlier this year, failed to take advantage of break-point opportunities in the opening game and never recovered.
"After that, I lost my rhythm and Yevgeny was all over me," Haas said.
Kiefer took 76 minutes to get past Slovakia's Dominik Hrbaty, 6-4, 6-3. Kiefer put himself in position to win a seventh career title.
"I had played my last final one year ago and this has been a tough season for me," Kiefer said. "It is only in my head that I have to be convinced that I can do it. It was only two years ago that I was in the top 10, won three titles and reached the semifinals of Hannover."
The men's finalists have split their two meetings this year.
In the women's draw, the eighth seeded Dementieva fought for two hours, nine minutes to overcome Myskina, 6-7 (7-9), 6-1, 7-5, and reach her second WTA final of the year.
The 19-year-old has enjoyed a strong run, having advanced to the semifinals of the Sparkassen Cup at Leipzig, Germany last week. Dementieva also reached the final of the Mexican Open claycourt event at Acapulco in March.
Dokic, the fifth seed, recorded a 6-4, 6-3 semifinal victory over Silvia Farina Elia of Italy, the eighth seed.
The 18-year-old Dokic is trying to capture her third WTA title of the year. She claimed the Italian Open crown in March and took the Princess Cup at Tokyo last month.
Dementieva outdueled Dokic twice in 2000. But Dokic finally broke through in the first round of this year's Pilot Pen hardcourt event in August.