Kreber topped the former World No. 1 from Serbia 6-1, 7-6 (8-6) to earn a berth in the finals of the $2.44 million tournament in Doha opposite Simona Halep of Romania.
Kreber hit a dozen winners while cruising through the first set and then held off Jankovic, who got on track in the second set, winning three straight games to force a tie-breaker.
The seventh-seeded Halep eliminated No. 2 seed Agnieszka Radawanska of Poland 7-5, 6-2.
The loss was the fourth in as many trips to the Qatar semifinals for Radawanska. Halep will play for her seventh title in 10 career finals.