Pamela Jelimo was born on 5th December 1989 in Nandi District, Rift Valley Province. Her mother, Esther Cheptoo Keter, was a promising 200 metres and 400 metres runner in her youth. Jelimo was raised by her mother in a family of three brothers and six sisters.
Jelimo began running in 2003, aged 13, at Koyo Secondary near Kapsabet. She won the the 100 metres, 200 m, 400 m, 800 metres, 400 metres hurdles, and heptathlons at schools’ championships. Her high school games teacher remarked that she used to compete with the boys in sprint events as the girls did not provide the competition she needed. She won the 400 metres gold medal at the African Junior Championships and set a Kenyan national junior record in the 200 m. Despite her budding athletics career, she continued to work at the Embu Police station as a police constable.
Her coach switched her to the 800m and she made her breakthrough at the 2008 African Championships in Athletics. On 25 May 2008 she set a new Junior World Record at the Hengelo Grand Prix event. It was also a new Kenyan record, previously held by Janeth Jepkosgei. On 1 June 2008 she ran an impressive 800 m race in Berlin and won the ISTAF Golden League in 1:54.99, a new African record. The previous African record (1:55.19) was set by Maria Mutola in 1994.
On 18 August 2008 Jelimo won gold in the 800 metres at the Beijing Olympics. Her time was 1:54.87, again a record. She became the first Kenyan woman to win an Olympic gold medal.Jelimo is also one of the youngest women to win an Olympic gold medal for Kenya.