Jamal Lewis joined Norwich as an academy scholar in the summer of 2014. . He was previously at Luton Town and nearly joined Brentford in 2011, two years after Luton dropped out of the Football League and were restricted in retaining players in their academy. A loophole kept Lewis at Luton until he parted ways with the Hatters to concentrate on his athletics career, finishing sixth in the 800m at the English Schools’ Championship at U17 level in 2013 and second in the English Schools’ U17 cross-country at Donington Park the following year.
In March 2016, he was called up to the Northern Ireland Under-19 squad
On 3rd May 2016, it was announced that Jamal had been offered a two year professional contract. He will be part of the development squad.
On 8th June 2017, Jamal played for Northern Ireland's Under-21s against Estonia. The Irish won 2-1
An impressive 2017 pre-season was cut short through injury but he returned and made his debut in the 2-1 home defeat to Brentford on 22nd December 2017. This was followed by his full debut in the 2-0 away win at Birmingham on 26th December 2017. His first professional goal was at Stamford Bridge in the FA Cup Third Round Reply when Lewis' 94th minute header drew Norwich level and took the tie into extra-time. Unfortunately Chelsea won on penalties.
In March 2018 he was called up to the full Northern Ireland squad for the first time. He made his debut on 24th March 2018 playing the full game in a 2-1 win over South Korea.
Lewis finished the 2017/18 season with 24 appearances and 1 goal. His form saw him linked on 27th June with Bournemouth and Watford whilst West Ham, Burnley and Celtic were said to be monitoring him. He is reportedly valued at £10m by Norwich.
On 26th March 2019, Lewis, along with Max Aarons and Teemu Pukki, were named in the Sky Bet Championship Team of the Season. The team was voted on by all 24 managers and head coaches from the Championship, with City having the highest representation in the eleven with three, ahead of Leeds United (2) and Sheffield United (2). He finished the 2018/19 season with 44 appearances as first choice as Norwich won the Championship title and promotion to the Premier League.
During the January 2020 transfer window, Lewis was linked with moves to both Liverpool and Crystal Palace.
He made 32 appearances during 2019/20, scoring once, as Norwich were relegated from the Premier League.
The speculation continued in July 2020 with Stoke City linked on 19th July in the Belfast Telegraph due to them being managed by former Northern Ireland boss Michael O'Neill. Two days later and football website Goal.com were linking Lewis with a move to Liverpool as cover for Andrew Robertson. Liverpool did indeed make a £10m bid but this was rejected by the Canaries who value Leiws at £20m. Liverpool then signed Greek full-back Kostas Tsimikas. Lewis was then linked with Leicester as a replacement for Ben Chilwell who was linked with Chelsea.
On 31st August 2020 the Daily Mail linked Newcastle United with a move for Lewis stating that Steve Bruce wanted to bring in homegrown talent but the report suggested Newcastle would struggle to meet Norwich's valuation. On 8th September Jamal completed his move to Newcastle for a fee of £15million plus add-ons that could take the final fee to £20million, Jamal signed a five year contract. He is the fifth player to join Newcastle in the 2020 summer transfer window afer midfielder Jeff Hendricks, winger Ryan Fraser, forward Callum Wilson and Scottish youngster Mark Gillespie. Bruce said "Jamal is a very exciting prospect. I watched him flourish in the Championship two years ago and he made a real fist of it in the Premier League last season."
On 25th August 2022 it was speculated that Norwich could seek to bring Lewis back to Carrow Road on loan following injuries to left-backs Dimitris Giannoulis, Sam McCallum and Jacob Sorensen. Lewis needs game time after having groin surgery earlier this year and Norwich would be able to provide it. Matt Targett is the first choice left-back on Tyneside whilst Dan Burn is also seen as being ahead of Lewis in the pecking order. French side Nice are also linked to having an interest.
He joined Watford on a season-long loan on 27th July 2023 having only made 36 appearances for the Magpies since joining them from Norwich.