He is the nephew of ex-professional football player Jay-Jay Okocha. Iwobi joined Arsenal while still at primary school, and was first involved in a first-team match as an unused substitute in a League Cup match against West Bromwich Albion on 25 September 2013. He signed a new long-term contract with Arsenal in October 2015.
On 27 October 2015, Iwobi made his first-team debut for the club, starting in a 3–0 defeat to Sheffield Wednesday in the Round of 16 of the League Cup.
On 19 March 2016, Iwobi scored his first senior goal in a 2–0 away victory against Everton. After playing youth football for England, Iwobi elected to play for Nigeria and made his senior debut on 8 October 2015, replacing Ahmed Musa in the 57th minute of a 2–0 friendly defeat to DR Congo in Visé, Belgium.