Aiwu spent seven years with his hometown club,
SKN St. Pölten, before joining
Admira Wacker in 2013. He came through the youth system to make his senior debut while still a 16-year-old, starting and playing the whole game for Admira II in the
Regional League East on 1 September 2017. He made 15 appearances for Admira II, contributed three goals from nine matches for Admira U18 as they went on to win the 2017–18 Jugendliga, found his way into the first-team squad and, towards the end of the season, started three
Bundesliga matches, the first coming in a goalless draw away to
Austria Wien on 5 May 2018. The following season, Aiwu was a first-team regular, The following day, Aiwu joined another Bundesliga club,
Rapid Wien, on a three-year contract. The fee was undisclosed. He made his debut on 15 September, starting in the home defeat against
Genk in the
Europa League group stage, and rarely missed a game thereafter. On 5 August 2022, Aiwu joined
Serie A club
Cremonese, newly promoted to
Serie A, on a four-year contract for a fee reported as €3.5 million. He played regularly for the first part of the season, but a mid-season change of management brought in a coach who preferred older, more experienced defenders, and although Aiwu was still a regular in the matchday squad, he rarely started. Despite his adviser's mention of interest from top-five leagues, and to
Burnley, newly returned to the
Premier League, Aiwu signed for English
Championship (second-tier) club
Birmingham City on 31 August 2023
on loan for the season. The deal included an option to purchase. ==International career==