Kostyuk broke away after an even start, winning three straight games to take the first set 6-3. Andreeva led 3-1 in the second set after two breaks, but Kostyuk rallied to level the score and closed out the match 7-5.
The victory marks the biggest title of the 23-year-old Ukrainian’s career.
Kostyuk advanced to the final with wins over Yulia Putintseva, Jessica Pegula, Caty McNally, Linda Noskova and Anastasia Potapova.
Kostyuk defeated Andreeva 2-0 (6-3, 7-5).
Kostyuk recently won a tournament in Rouen, beating fellow Ukrainian Veronika Podrez in the final.
Other Ukrainian players have also posted strong results in recent months. Daria Yesypchuk won the ITF W15 event in Tunisia in April. Daria Snigur claimed the ITF W75 title in Slovenia in March and earlier won a WTA 125 tournament in Portugal, securing the biggest title of her career. Katarina Zavatska won the ITF W35 event in Spain, while 19-year-old Yelyzaveta Kotliar captured the ITF W15 title in France.
Angelina Kalinina, a former Ukrainian No. 1, also won her second WTA title in Antalya, defeating her opponent decisively in the final after claiming another title earlier in March against compatriot Oleksandra Oliynykova.