Kirui outran Galen Rupp of the U.S. to take the men's race in an official time of 2 hours, 9 minutes, 37 seconds. Rupp, also running his first Boston, trailed by 21 seconds.
Kiplagat opened up a big lead heading into the dreaded Newton Hills and won in an official 2 hours, 21 minutes, 52 seconds.
Jordan Hasay, racing her first ever marathon, finished third, and fellow American Desi Linden was fourth.