Sharapova, seeded fourth, battled back to take down the 13th-seeded Jankovic 4-6, 7-6 (7-3), 6-3.
Sharapova claimed her second title this year and 24th of her career.
Jankovic, who won the Cincinnati title in 2009, was trying for her 13th career title and first this year. She fell to 1-6 all-time against Sharapova. This was their fourth encounter in a final.
Sharapova took home $360,000 with the victory.