At age 14, she was recruited as a 200 and 400 metres sprinter to attend Riruta Central Secondary School in Nairobi.

[4] She is married to Tom Nyaundi, a former runner, and they have a daughter, Tania 'Blessing' Macheche, born in May 2015 through caesarean section.

She debuted in the World Championships in Athletics held in 2011 in Daegu, South Korea the following month, competing at the latter distance.

Obiri set a personal best time of 4:07.59 in the heats but fell in the final, bringing pre-event favourite Morgan Uceny down with her, and finished 10th.

That same year, she debuted in the Olympics at the London Games, finishing initially 12th and last in the 1500 m final, upgraded to eighth after subsequent doping disqualifications.

[citation needed] On 1 June 2013, Obiri won her first Diamond League race with 1500 m victory in Eugene, setting a new personal best and meet record of 3:58.58.

On 9 May that year at the Doha Diamond League, she set an African record in the outdoor event with a time of 8:20.68, improving her personal best by more than 13 seconds.

[6] Obiri represented Kenya at the 2017 World Championships in London in the same event and won the gold medal with a time of 14:34.86, ahead of Ayana and Sifan Hassan.

[1] In March 2019, Obiri won the senior women's race at the World Cross Country Championship held in Aarhus, Denmark, beating on a 10.2 km course second-placed Dera Dida by two seconds with a time of 36:14.

[13] At the 2022 World Championships in Eugene, Oregon, Obiri came second in the 10,000 m. She was beaten to gold by Gidey in a close finish (the top 3 were only separated by 0.13 s).