The top-seeded Cilic will be seeking his third Zagreb title Sunday when he battles No. 4 seed Austrian Jurgen Melzer in the finals.
Cilic, who won the tournament in 2009 and 2010, knocked off No 3 seed Youzhny 4-6, 6-4, 6-3.
Melzer advanced with a 7-6 (7-2), 6-3 win over Robin Haase of the Netherlands.
Florida bear attack: Black bear mauls woman's face
Texas principal bans speaking Spanish, stirs controversy