[5] On 26 January 2024, Mills ran a personal best time of 12:58.68 in the indoor 5000m at the BU John Thomas Terrier Classic.

Mills came in 2nd place in the Scarlet Heat, ahead of Yared Nuguse (13:02.09) and behind Edwin Kurgat of Under Armour (12:57.52).

[6][7] On 11 February 2024, Mills finished 3rd in the NYRR Wanamaker Mile, in an indoor personal best time of 3:48.93.

[8] At the 2024 European Athletics Championships Mills won a silver medal in the 5000m behind Jakob Ingebrigtsen.

[9] After winning the 1500 metres silver medal at the 2024 British Athletics Championships, Mills was subsequently named in the Great Britain team for the 2024 Summer Olympics.