Korir, who graduated from nearby Iona College with a degree in political science in 2012, won the 21.1 km race in a time of 1:01:06.
Stephen Sambu, 26, who finished third with a time of 1:01:18 at last year's NYC half marathon, improved his performance to take second place in 1:01:07 ahead of Mexico's Juan Luis Barrios, who took third in 1:01:14.
Leonard Korir, 28, is often misidentified as Wesley Korir - the 32 year-old 2012 Boston Marathon champion and a two-time winner of the Los Angeles Marathon (2009, 2010) - who was elected Member of Parliament for Cherangany Constituency in March 2013.
“You know, most people don’t know me,” Leonard Korir said, grinning slightly after the race. “I think I was like a dark horse. Nobody knew I was going to win.”
“I wanted to give all I could to win this race because I love this place,” Korir added.
Kenyan women stunned
American Molly Huddle tied the course record with a time of 1:08:31 to win the women's race, beating the highly-fancied Kenyan duo of Joyce Chepkirui (1:08:42) and defending champion Sally Kipyego (1:09:39) to the second and third positions respectively.
Korir’s victory simply upheld Kenya’s dominance to four years in a row after Peter Kirui (2012), Wilson Kipsang (2013) and Geoffrey Mutai (2014).
Last year’s Geoffrey Mutai of Kenya won the men's race with a time of 1:00:50, and Sally Kipyego won the women's race with an event-record time of 1:08:31.
Ernst van Dyk, the 41-year-old South African, won the men's wheelchair race in 48 minutes and 54 seconds.
A total of 20,828 runners crossed the finish line, making it the biggest half marathon. Runners from more than 65 countries and all 50 US states participated.
Korir and Huddle each earned $20,000 for their victories, with van Dyk and Schär each taking home $4,000.