Germany's Haas advanced to the final with a 5-7, 6-4, 6-3 decision over unseeded Daniel Evans, who made the tournament as a "lucky loser" and mounted a surprising run through the field.
The 35-year-old Haas will be seeking his 16th career title against three-time Zagreb champ Cilic, who breezed past German qualifier Bjorn Phau 6-3, 6-4 in Saturday's other semifinal.
Cilic, the fifth seed, won the event last year as well as in 2009 and 2010. He is 9-8 in title matches.
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