He was signed by Arsenal in the summer of 1948 for £10,500, as backup for Reg Lewis, who was only 28 but becoming ever more frequently injured. Lishman made his debut against Sheffield United on 4 September 1948, but after a promising first season (scoring 13 goals in 25 appearances), Lishman's 1949–50 and 1950–51 seasons were marred by injury. Lishman was passed over for the 1950 FA Cup Final (which Arsenal won 2–0), in favour of Lewis and Peter Goring, and then just as he came back into the Arsenal first team, he broke his leg playing against Stoke City in December 1950.