Diangana was born in the Democratic Republic of Congo. His family moved to the United Kingdom when he was four years old. Diangana grew up in Woolwich, London.
Diangana joined the West Ham youth system in 2010, aged 12. Originally a striker, he began playing as an attacking midfielder at under-15 level. He made his under-18 debut for the club in February 2014, and his Premier League 2 debut in January 2015. He signed his first professional contract with the Hammers on 14 May 2016. He signed a new two-year contract in June 2018.
On 26 September 2018, Diangana made his first team debut in the EFL Cup against Macclesfield Town, playing the full game and scoring two goals in an 8–0 victory at the London Stadium, in which fellow debutants Conor Coventry and Joe Powell also featured. Three days later, Diangana made his first Premier League appearance, coming on as a 93rd minute substitute for Felipe Anderson in a 3–1 home victory against Manchester United. Diangana became a regular in the team following an injury to Andriy Yarmolenko, making his first Premier League start against Leicester City on 27 October and registering his first league assist in the following game, against Burnley. On 18 January 2019, Diangana signed a new six-year contract that keeps him at West Ham until 2025.
Loan to West Bromwich Albion
On 8 August 2019, Diangana joined West Bromwich Albion on loan until the end of the season He made his West Brom debut on 13 August 2019 in a 2–1 home defeat by Millwall in the first round of the EFL Cup. Diangana scored his first two goals for West Brom on his league debut, on 17 August 2019. Coming on at half-time for Kyle Edwards against Luton Town, scoring two goals in six minutes in a 2–1 win which ended Luton's run of 28 home games unbeaten.
In November 2018, Diangana received his first international call-up, for England U20, for a game against Germany U20. He made his England debut on 19 November in a 2–0 win against Germany. In September 2019, Diangana was called into the England U21 team for the first time, for matches against Turkey U21 and Kosovo U21 after impressing with 3 goals in his first four matches on loan in the Championship with West Bromwich Albion.
Style of play
Diangana generally plays as a right-sided attacking midfielder but can play across the forward line. He cites Ronaldinho as an influence