[3][4] Competing at the British Athletics Championships in July 2023, in Manchester, England, she reached the final of the women's 400m and finished in 3rd place.

[8] Running the anchor leg in the mixed 4 x 400-metre relay, she took advantage of a late, dramatic fall by Femke Bol of the Netherlands to win world silver, her first senior representative medal.

After winning the 400 metres bronze medal at the 2024 British Athletics Championships, John was subsequently named in the Great Britain team for the 2024 Summer Olympics.

Again running the heats only, she won an Olympic bronze medal as part of the successful Great Britain women's 4 x 400 metres relay squad.

[10] Yemi has a Nigerian father (Christopher Olanrewaju John) and an Italian mother (Gabriella Faciotti) who lives in London.