[12] At the 2019 World Championship, Humphries had his breakthrough event on television, beating Adam Hunt, Stephen Bunting, Dimitri Van den Bergh, and defending champion Rob Cross,[13] before eventually losing to Michael Smith in the quarter-finals.

[16] At the age of 24, Humphries won the 2019 PDC World Youth Championship, where he beat Adam Gawlas 6–0 in the final.

[19][20] Humphries was the winner of PDC Home Tour 2 after winning five of his six Championship Group matches, beating Jonny Clayton based on leg difference.

His run to the final saw him claim wins over Dave Chisnall in the quarter-finals and then-reigning champion Michael van Gerwen in the semi-finals.

[28] In October, Humphries won his first major title at the 2023 World Grand Prix, defeating tournament favourite Gerwyn Price 5–2 in the final.

[30] He won his second major televised title 42 days later at the 2023 Grand Slam of Darts, defeating Rob Cross 16–8 in the final with a three-dart average of 104.69.

He came back from 9–5 down to defeat Michael van Gerwen 11–9 in a match where van Gerwen hit a nine-dart finish but missed eight darts at doubles in the 19th leg to set up a deciding leg, before Humphries won the match on double 1.

On 3 January 2024, Humphries won the World Championship, winning five sets in a row to defeat fellow Cheshire talent Luke Littler 7–4 in the final.

[39] Humphries represented England for the first time in the World Cup of Darts in June, partnering Michael Smith.

[44] In October, Humphries started his defence of the World Grand Prix after his victory over Gerwyn Price in the 2023 final.

[47] In November, following elimination in the group stage of the 2024 Grand Slam of Darts,[48] Humphries successfully defended a title for the first time at the 2024 Players Championship Finals, defeating Luke Littler 11–7 in the final, becoming only the third player in history to win the title in 2 consecutive years, after Taylor and van Gerwen.

[62] Humphries announced he would raffle off his match-worn shirt from night fifteen and donate the proceeds to the Rob Burrow Foundation, a charity for motor neurone disease.

[66][67][68] At the 2025 World Championship, Humphries began his title defence with a 3–0 whitewash win over Thibault Tricole followed by a 4–0 victory against Nick Kenny, setting up a fourth round tie against Peter Wright.

Wright stated that he was ready to upset tournament favourites Humphries and Luke Littler, claiming that he could compete with and be better than them despite calls for him to retire.

"[69][70] In their match, Humphries leveled the contest at 1–1 before dropping the next three sets to lose to Wright 4–1, ending his tenure as world champion.

[71] In February, he won the PDC World Masters, defeating Jonny Clayton 6–5 to win his seventh major title.

[75] Humphries began a weight loss journey in 2021 in order to improve his fitness and stamina, which led to him losing four stone (56 pounds).

[4][77] On 30 May 2024, whilst in New York for the 2024 US Darts Masters, the couple became engaged, with Humphries proposing to her on the top floor of The Edge.