Karlovic, seeded fourth, has won his last nine matches in the tournament but was pushed hard by eighth-seeded Gael Monfils. Karlovic's powerful serve was working as he had 11 aces and was broken just once in taking the 7-6 (7-4), 7-6 (7-4) victory.
He will face third-seeded Fernando Verdasco, who had no trouble in getting past Marin Cilic 6-3, 6-1 in his semifinal.
Karlovic, 3-2 in finals, is seeking his first title of 2008 while Verdasco is 1-3 in ATP finals. It is his first final of the year and first on a grass court. Verdasco and Karlovic have split their two previous meetings.