[1] The following month, at age 17, he moved to Albuquerque and began competing for the University of New Mexico, majoring in exercise science.

In August 2019, he participated in the 1500 m at the British Athletics Championships, where he secured a silver medal, finishing behind Neil Gourley.

[13] This victory secured his spot to represent the British team at the 2020 Summer Olympics in Tokyo, which were rescheduled to 2021 due to the COVID-19 pandemic.

At the Olympic 1500 m final, Kerr won a Bronze medal in a personal best of 3:29.05, finishing behind Norway's Jakob Ingebrigtsen and Kenya's Timothy Cheruiyot.

[17] On 23 August 2023, Kerr defeated Norwegian favorite Jakob Ingebrigtsen in the final of the 1500 metres at the 2023 World Athletics Championships.

[18] Later that month, on 31 August 2023, Kerr competed in the Diamond League Final for the 1500 m, aiming to break the British record.

In his final race of the season on 10 September 2023, Kerr won the New Balance 5th Avenue Mile, clocking a time of 3:47.9.

[22] In his first race of the year on 11 February, Kerr set a world best in the short track 2 mile at the Millrose Games.

On 2 March, Kerr ran 7:42.98 for 3000 metres to claim gold at the World Athletics Indoor Championships in Glasgow, Scotland.

[24] On 20 April, Kerr opened his outdoor season in the Pro Men's 800m Challenge at the Oregon Relays, winning in a time of 1:45.94.

[25] On 25 May, at the Prefontaine Classic, Kerr won the Bowerman Mile in a new British record time of 3:45.34, ahead of Jakob Ingebrigtsen (3:45.60) and Yared Nuguse (3:46.22).

[28] Just days earlier it was announced that he had signed up for the inaugural season of the Michael Johnson founded Grand Slam Track in 2025.

[32][33][34] The final at these Games was anticipated because of Kerr's rivalry with fellow European middle-distance runner Jakob Ingebrigtsen.

This eclipsed Sydney Maree's previous record of 3:47.52 by more than three seconds, which had stood for 43 years, since the inaugural edition of the race in 1981.