Carlisle United Branthwaite started his career with
Carlisle United's youth system aged eight and signed his first professional contract, of two years with an option to extend, in February 2019. His first involvement with the
first team came as an unused
substitute on 16 March in a 1–1 draw away to
Forest Green Rovers. He appeared on the bench for seven more consecutive
League Two matches that season. He scored his first goal for Carlisle in an
EFL Trophy tie against
Morecambe on 12 November.
Everton 2020–2022 On 13 January 2020, Branthwaite signed a two-and-a-half-year contract with
Premier League club
Everton, keeping him at the club until the end of June 2022. He made his debut on 12 July, coming on as a substitute in a 3–0 defeat against
Wolverhampton Wanderers. He made his home debut against
Aston Villa on 16 July, coming on as a substitute for the second straight game, this time for the injured
Mason Holgate in the 16th minute. Branthwaite started his first game for Everton on 20 July against
Sheffield United after signing an extended contract until June 2023, in which he was named man of the match in a 1–0 win for Everton. On 14 January 2021, Branthwaite joined
Championship club
Blackburn Rovers on
loan for the rest of the
2020–21 season. He made his debut two days later, starting and playing the full ninety minutes in a league game against
Stoke City that finished 1–1. Branthwaite's season was ended prematurely on 21 April when he suffered an ankle injury during training. In total, he played in ten league games, all starts, for Rovers, including nine straight after joining on loan. On 16 December 2021, Branthwaite made his first Premier League start of the season and scored his first Everton goal in a 1–1 away draw against
Chelsea.
2022–present On 17 July 2022, Branthwaite joined
Eredivisie club
PSV Eindhoven on a season-long loan. He scored an
own goal in the
2023 KNVB Cup final against
Ajax. PSV eventually lifted the trophy after winning a penalty shoot-out. Branthwaite started in Everton's third
Premier League fixture, a 1–0 loss to Wolverhampton Wanderers on 26 August 2023. After his appearance against Wolves, he continued to start in central defence, forming a partnership with team captain
James Tarkowski. On 6 October 2023, he signed a new contract with Everton running until June 2027. Branthwaite scored his first goal of the 2023–24 season on 3 February 2024, with an 94th minute equaliser against
Tottenham Hotspur in a 2–2 home draw. At the end of the 2023–24 season, he was voted as Everton's Players' Player and Supporters' Young Player of the Season. ==International career==