Trueman was born in Birmingham and attended King Edward VI Aston School. He joined Birmingham City's academy in 2007, and took up a scholarship in July 2012. He signed his first professional contract, of one year with the option of a second, in June 2014. When first-choice goalkeeper Darren Randolph had to miss the visit to Blackburn Rovers in October 2014 through suspension and previous third-choice Nick Townsend's loan had no recall clause, Trueman was given a squad number and a place among the substitutes; he remained unused. He then spent time on loan at Leamington, for whom he played twice in the Conference North and once in the FA Trophy. At the end of the 2014–15 season, Birmingham took up their option for another year on Trueman's contract, and in April 2016, he signed a one-year contract, with the option for a further year. He made his first appearance of the season in a matchday squad on 30 April, at home to Middlesbrough, when Adam Legzdins took over in goal after Tomasz Kuszczak underwent surgery on a broken nose, and kept his place on the bench for the last match of the campaign, away to Cardiff City. In between, he was an unused substitute for the Birmingham reserve team that lost the 2016 Birmingham Senior Cup final to National League North champions Solihull Moors. On 13 September 2016, away to Reading, Kuszczak was injured during the warm-up, so Legzdins took his place in the starting eleven and Trueman was added to the substitutes. He retained his place in the matchday squad for a further four league matches while Kuszczak recovered. He signed a new three-year contract in May 2017. When David Stockdale joined in 2018, Trueman dropped to fourth choice, and went on loan to Solihull Moors until January 2018. An injury to Stockdale in September left the club with only one fit professional goalkeeper, so Trueman was recalled to act as backup to Kuszczak. When Stockdale returned to the starting eleven in November, manager Steve Cotterill retained Trueman in the matchday squad, but when Garry Monk took over in March, he recalled Kuszczak to the bench. At the end of the season, Monk told both Stockdale and Kuszczak they were free to find other clubs, and neither took part in the first team's pre-season training. A bid for Ipswich Town's Bartosz Białkowski came to nothing, and Trueman went through pre-season as first-choice goalkeeper. He made his Football League debut in the starting eleven for the opening match of Birmingham's 2018–19 season, a 2–2 draw at home to Norwich City in the Championship, and despite the arrival of the experienced Lee Camp kept his place for the visit to Middlesbrough. According to the Birmingham Mail, Trueman "had no chance with a superbly struck goal but all at sea on a couple of occasions", and Camp took over for the next match and the rest of the season, with Trueman as a regular on the bench. With Birmingham safe from relegation, he was due to start the final match of the season, away to Reading, but illness prevented his appearance. Trueman signed a two-year contract extension ahead of the 2019–20 season.
