Petkovic, an unseeded wild-card entrant for the tournament in her home country, defeated Jankovic 6-4, 6-3. She had three breaks in each set and ended up winning 58 percent of the points off Jankovic's serve.
Petkovic won 54 percent on serve and fought off eight of the 12 breaks points she faced. Eight of those were in the second set when she won all three of her own break opportunities.
Halep, the No. 7 seed, came away a 6-3, 0-6, 6-2 winner over fifth-seeded Lucie Safarova. After a tight first set, Safarova controlled the second set, losing only three points on serve. But Halep didn't face a break point in the third set and moves into the finals.
The championship match of the inaugural Nurnberger Versicherungscup will mark the first career meeting between Petkovic and Halep.
Petkovic is 2-3 in championship matches, with her most recent win coming in October 2011 in Strasbourg, France. Halep is 0-3 in WTA title matches, with one such appearance each of the last three years.