She trailed Buzunesh Deba by nearly 3 1/2 minutes at the halfway point. Jeptoo started making her move as the race entered Manhattan and passed Deba with just more than 2 miles to go.
Jeptoo won in an unofficial time of 2 hours, 25 minutes, 7 seconds Sunday. The London Marathon champ clinched a $500,000 bonus for the World Marathon Majors title.
An Ethiopian who lives in the Bronx, Deba finished second for the second straight NYC Marathon.
The 26.2-mile race returned after a one-year absence, cancelled in 2012 because of the destruction of Superstorm Sandy.
Security was heightened after the bombings at April's Boston Marathon. Bomb-sniffing dogs roamed the course, and barricades limited access points to Central Park.