Kimetto, who also won the Tokyo Marathon this year, ran the Chicago course in 2 hours, 3 minutes and 45 seconds, bettering Ethiopian Tsegaye Kebede's 2012 mark of 2:04:38.
All top four spots in the men's race were claimed by Kenyans -- second-place Emmanuel Mutai finished 7 seconds off the pace, followed by Sammy Kitwara and Micah Kogo.
Jeptoo, meanwhile, finished at 2:19:57, fully 51 seconds ahead of countrywoman Jemima Sumgong Jelegat on the women's side.
Jeptoo missed the Chicago title by just 1 second in last year's event when she finished just behind Ethiopia's Atsede Baysa.
A total of 39,115 runners crossed the finish line in Grant Park under ideal weather conditions.
Millions of Getty images now available for free via embed tool
Aaron Carter is still in love with Hilary Duff