Dulwich Hamlet youngster Diallang Jaiyesimi played for Norwich City's Under-18s in their 7-0 defeat to Chelsea on 31st October 2015. He then played and scored against Arsenal in November and featuring in victories over West Ham United and Leicester City.
On 2nd January 2016, he signed a two and a half year contract with Norwich, joining as a second year scholar. City fought off competition from several other Premier League clubs to sign Jaiyesimi, who was captain of Dulwich's FA Youth Cup side this season while also making five appearances for their first-team
Diallang scored eight goals in 33 games for Norwich's Under-23s in 2016/17.
On 9th August 2017 he joined Grimsby Town on a season long loan. Norwich's former youth development coach Paul Wilkinson is Assistant Manager at Grimsby. Diallang has been handed the number 20 shirt. Mariners' manager Russell Slade said “We’ve watched him play recently in a pre-season game against Sutton and he was really outstanding. Powerful, really quick, can play on the left, can play on the right and can play number 10. He made his league debut for Grimsby on 12th August 2017 in a 2-0 defeat to Coventry.
On 25th August 2017, he was charged with drink-driving and banned from driving for 18 months after being caught more than twice the legal alcohol limit in Norwich. He was fined £485 and banned from driving for 18 months, with a victim surcharge of £48 and costs of £85.
Jaiyesimi netted the first goal of his professional career on Tuesday night, scoring for Grimsby Town against Scunthorpe United in the 32nd minute in the Checkatrade Trophy Northern Section Group H match.
He signed a new contract with Norwich on 15th November 2017 until 2020. He had played 15 games for Grimsby at that time.
He finished the season having played 35 times for Grimsby although 25 of those were as substitute. He was then loaned to Yeovil for the 2018/19 season on 20th June 2018. After scoring twice in eleven appearances, a knee injury ended his season.
In July 2019, it was reported that Portsmouth, Cambridge and Wycombe were keen on signing him on loan. On 2nd August 2019 Diallang joined League Two Swindon Town on a season-long deal. He made his Swindon debut the following day as an 80th minute substitute against Scunthorpe.