Her highest Olympic finish individually was fourth in the 200 metres at the 2024 Games, missing a medal by two-hundredths of a second.

[14] At the 2012 World Junior Championships, Asher-Smith finished seventh in the 200 m final in a then personal best time of 23.50 seconds.

The British squad originally finished fourth in the final but were promoted to the bronze medal after the disqualification of the French team.

Along with teammates Annabelle Lewis, Ashleigh Nelson and Hayley Jones, she won a bronze medal in the 4 × 100 m relay.

At the 2016 Summer Olympics in Rio de Janeiro, Asher-Smith finished fifth in the 200 metres, in a season's best of 22.31 seconds, then won a bronze medal with her teammates Asha Philip, Desiree Henry and Daryll Neita in the 4 x 100 m relay in a British record of 41.77 seconds.

[25][26] On 17 February 2017, Asher-Smith broke her foot in a training accident,[27] but still managed to secure fourth place in the women's 200 m[28] and a silver medal as part of the Great Britain 4 × 100 m relay later that year at the World Championships in London.

In 2018, she went to Australia early to train and get used to the conditions prior to the Commonwealth Games scheduled to take place in Gold Coast, Queensland in that country.

England ladies, including Asher-Smith, qualified for the 4x100 m relay final, where they won gold in a time of 42.46 seconds, beating one of the favorites, Jamaica.

[30] Three days later, she continued her good form by winning the Stockholm Diamond League in 10.93 s.[31] At the 2018 European Championships in Berlin, Asher-Smith won both the 100 m[32] and 200 m titles, improving her British records to 10.85 and 21.89 seconds respectively, becoming the first British woman in history to run below 22 seconds for 200 metres, and moving to 22nd on the 200 metres world all-time list (35th at 100 m).

[42] She was the first female British sprinter to win, over 100 m or 200 m, an individual medal in the world championships since Kathy Cook in 1983.

Her season was off to a promising start in May when she won the women's 100 m final at the Gateshead Diamond League against a world class field, besting athletes such as Shelly-Ann Fraser-Pryce, Blessing Okagbare, Marie-Josée Ta Lou and Sha'Carri Richardson.

Subsequently, she revealed in an emotional interview that she had actually sustained a hamstring injury during the finals of the British Championships, and that she would be pulling out of the 200 m.[47] Nevertheless, she managed to return to contribute to the 4 x 100 m relay, aiding Great Britain in setting a new national record of 41.55 seconds in their heat, followed by a bronze medal in the final behind Jamaica and the United States.

[51] In 2022, Asher-Smith ran her first Diamond League of the season in Doha, placing third over 200 m behind Gabby Thomas and Shericka Jackson in a time of 22.37 s.[52] She won the 100 m at the Birmingham Diamond League in a time of 11.11 s, narrowly beating out Shericka Jackson and Daryll Neita.

[53] At the 2022 British Athletics Championships, she was beaten by Neita in the 100 m.[54] She recovered to win at the Stockholm Diamond League over 200 m, in a time of 22.37 s.[55] At the World Athletics Championships in Eugene, Asher-Smith placed fourth in the 100 m, equalling her British record of 10.83 s.[56] She went on to win a bronze medal in the 200 m, having run her first sub-22 second 200 m since 2019 in the semi-finals.

[58][59] In August, she competed at the European Championships, in the 100 m, Asher-Smith struggled with cramp as she pulled up after 60 m and finished eighth in the final.

[62] She broke the record again on 25 February, running 7.03 s in the heats of the World Indoor Tour Final in Birmingham, she went on to win the final in 7.05 s.[63] She won the 100 m at the 2023 British Championships in a time of 11.06 s.[64] On 23 July, Asher-Smith ran 10.85 s in finishing second at the London Athletics Meet, this time was just 0.02 s off of her national record.

[65] At the 2023 World Athletics Championships after a season impacted by minor injuries, Asher-Smith finished eighth in the 100m final and seventh in the 200m.

[70] After winning the gold medal in the 200 metres at the 2024 British Athletics Championships, Asher-Smith was subsequently named in the Great Britain team for the 2024 Summer Olympics.