After dropping the first set 4-6, Sharapova took the middle set 7-6 (7-3) and then forged the win over the 13th-seeded Serb with a 6-3 third set.
The former world No. 1 claimed her second title of the year and 24th of her career. She was last year's runner-up at Cincinnati, losing to U.S. Open champ Kim Clijsters in the final.
Jankovic, who won the event in 2009, fell short in her bid for her 13th career title and dropped to 1-6 all-time against Sharapova.