Iyogun captained the Northampton Saints under-18s as a back row forward prior to being converted into a front row forward.[4] He played in the RFU Championship on loan at Bedford Blues.[5]
On 13 September 2020 whilst still a teenager Iyogun made his Premiership debut as a substitute and a week later made his first start in their European Rugby Champions Cup quarter-final elimination against Exeter Chiefs.[4][6] He was named the Club’s Breakthrough Player of the Season in his debut campaign in 2019-20.[7]
Iyogun had made 25 appearances by the end of the 2021-22 season, including a start in the Premiership semi-final defeat to Leicester Tigers.[8] He signed a new long-term contract with the club in August 2022.[9] In January 2023, he suffered an Achilles injury which ended his season.[10]
In May 2024 Iyogun was part of the side that were eliminated by Leinster at the semi-final stage of the Champions Cup.[11] The following month saw him come off the bench as a substitute during the 2024 Premiership final as Northampton defeated Bath to become league champions.[12]