At the age of 17, Stewart received his first call-up to the senior squad at the club (now renamed Airdrieonians) in August 2013,[1] making his senior debut two months later in a 2–0 home defeat to Forfar Athletic in Scottish League One, with his first start in the competition against Stranraer in March 2014.[3] He initially began his career as a midfielder but retrained as a full-back, which he stated drew more scrutiny on his performances from his father, who had played the same position.[4] After three seasons as a squad member, he became a regular starter for the Diamonds in the 2016–17 campaign, going on to make over 100 appearances over the next three years,[1][5] including a promotion playoff semi-final defeat to Alloa Athletic on penalties in 2017[6] (the closest Airdrie came to either being promoted or relegated in his time with the club) and a Scottish Cup visit to holders Celtic in 2019.[7]
He was voted the Airdrieonians 'Young Player of the Year' for 2016–17[8] and the overall 'Player of the Year' for 2017–18,[8] having been named team captain in the latter part of that season[9] and agreed a new contract to stay at the club.[10]
