Cilic won the Zagreb Indoors for a fourth time last week, and has beaten top-10 players Andy Murray and Jo-Wilfried Tsonga in Rotterdam.
Sijsling, the Dutch wild card, had raucous support from the crowd, especially after breaking Cilic twice in the first set, but he couldn't capitalize on the only break point he had in the second. He didn't get any in the third.
The unseeded Cilic, aiming for a 12th ATP title, has a losing 2-4 record against Berdych, who will be playing for ninth career title.
Berdych was more consistent than Gulbis, especially on serves, though Gulbis was often better -- if unpredictable -- in the rallies.
In the first set, Berdych won a 15-shot rally to set up a single break point, which he also won. The pair exchanged words after Gulbis issued a late challenge as to whether Berdych's return was in.
"Probably it looks on paper that it was easy, but it definitely was not," Berdych said after improving to 4-2 against Gulbis. "I was more calm, more focused, and that was my advantage."