He has won four other major titles: the Premier League, Grand Slam and World Series Finals all in 2024, and the 2025 UK Open.

In 2025, Littler reached the final for a second consecutive time, where he defeated Michael van Gerwen to win the title.

Littler is the youngest player to hit a televised nine-dart finish, which he achieved at the 2024 Bahrain Darts Masters two days before his 17th birthday.

His rise to prominence at age 16 led to an increased interest in the sport, a phenomenon dubbed "Littlermania" or the "Littler effect".

In November 2021, Littler won his first seniors title at the Irish Open defeating Barry Copeland 6–2 in legs.

[11][12] Littler won the JDC Super 16 in Milton Keynes at the end of January 2022, beating Eleanor Cairns in the final.

[14] At the 2022 WDF World Darts Championship, Littler started as a seeded player from second round and won his first match against Ben Hazel 3–2 in sets.

At the 2022 WDF Europe Cup Youth, he won the gold medal in three men's competitions (singles, team and overall).

Littler won the JDC World Darts Championship in London at the end of December 2022, beating Harry Gregory 5–0 in legs.

[26] Littler reached the fourth round, the best showing of a Rileys qualifier at the tournament alongside Thomas Banks.

[32][33][34][35] On 26 November, Littler beat Gian van Veen 6–4 in the 2023 PDC World Youth Championship final.

[36][37] The next month Littler retained his JDC World Darts Championship title, defeating Álmos Kovács 5–3 in the final.

[38] In May 2023, Littler won the third season of the MODUS Super Series, defeating Jacob Taylor 4–1 in legs in the final.

[39] In August 2023, he won the fourth season of the MODUS Super Series, defeating Colin Osborne 4–2 in the final.

[48] This made him the youngest player to reach the PDC World Darts Championship final, as he was aged 16 years and 347 days.

[56][57] He won his second World Series title at the Poland Darts Masters, beating Rob Cross 8–3 in the final.

[58] As he had gained a PDC Tour Card, Littler played at his first Players Championship series, winning three titles.

[86][87] Littler qualified for the final by defeating Meikle, Ian White, Ryan Joyce, Nathan Aspinall and Stephen Bunting.

In the final on 3 January 2025, Littler defeated three-time world champion Michael van Gerwen 7–3 in sets.

[91] He broke £1,000,000 on the PDC Order of Merit for the first time and moved up to a career highest ranking of second in the world, behind Luke Humphries.

[98] Using darts manufactured by Target with characteristically long 45mm points,[99] Littler plays at a quick pace[98] and is known for his efficiency in checking out on the double 10 segment.

[111][112][113] Littler was named BBC Young Sports Personality of the Year in 2024, becoming the first darts player to receive the award.

[114] He also finished as runner-up for BBC Sports Personality of the Year behind 2024 Summer Olympics gold medalist Keely Hodgkinson.

[120] In March 2024, he made an appearance on the 232nd episode of The Jonathan Ross Show alongside Rob Beckett, Millie Bobby Brown, Liam Gallagher, Raye, and John Squire.

[123] The clip went viral after viewers of the show were amused by his nonchalant reaction to Brown admitting to being a huge fan of him.

[125][126] Following his 2025 World Championship win, Littler paraded his trophy at Old Trafford during half-time of Manchester United's match against Brighton & Hove Albion on 19 January 2025.