Prior to that she was a junior silver medallist at the 2008 World Cross Country Championships and represented Kenya in the senior race in 2013 and 2015, winning team medals both times.

Irene Chepet Cheptai made her international debut at the 2007 World Youth Championships in Athletics, where she ran a personal best of 9:22.05 minutes to place seventh overall in the 3000 metres.

[1] The following year she established herself internationally on grass by taking the silver medal in the junior race at the 2008 IAAF World Cross Country Championships, losing only to Ethiopia's Genzebe Dibaba in a sprint finish.

[10][11] On the 2015 IAAF Diamond League circuit, she placed in the top six of the 5000 m at the Shanghai Golden Grand Prix, Prefontaine Classic and Bislett Games.

[13] At the 2017 IAAF World Cross Country Championships Cheptai won individual and team gold, in a historic event in which Kenya secured the top six positions in the senior women's race.