Former Arsenal youngster Nathan Tella played on trial for Norwich's Under-18 against Reading on 18th February 2017. He had trialled with Reading the previous week and joined Southampton in March 2017. He had been at Arsenal for 10 years. He had grown up in Stevenage.

He made his Southampton debut on 19th June 2020 against Norwich. His first league goal was against Fulham on 15th May 2021.

On 11th August 2022 he signed for Burnley on a season-long loan. He had played 41 games for Southampton at the time of the loan, scoring twice.

Tella and Burnley won promotion to the Premier League on 7th April 2023. His contribution was 19 goals.

Although Burnley wanted to sign him permanently, Southampton sold him to German side Bayer Leverkusen on 27th August 2023 for a reported £20million. "Although disappointed to lose such a talented homegrown player and popular character, the club felt the offer represented fair value," said Southampton.

Tella said "Many younger players from the Premier League got a chance in the Bundesliga and were able to improve significantly here. This is an impressive team who made it to the semi-finals of the Europa League last season. I really want to continue on this path with Bayer 04." He made his first appearance for Leverkusen on 2nd September 2023 in a 5-1 win over SV Darmstadt. His first goal came against Molde in the Europa League on 5th October 2023.

In his first season with Leverkusen, they won the Bundesliga with a 5-0 win over Werder Bremen on 14th April 2024. They also reached the final of the German Cup and the semi-finals of the Europa League. Tella made 20 Bundesliga appearances, scoring five goals. Although they lost the Europa League final 3-0 to Atalanta on 22nd May 2024, they won the German Cup and thus the double on 25th May 2024 beating Kaiserslauten 1-0 with Tella coming on as a 94th minute substitute. This was the first time Leverkusen had won the German Cup since 1993.

In November 2023 he was called up by Nigeria for their World Cup qualifiers against Lesotho and Zimbabwe. He made his debut against the latter on 19th November 2023.