He left Northampton in May 1958 to join First Division side Leicester City for a fee of £10,000 as an inside left or outside left. The same summer, he travelled with the Welsh national side to Sweden for the World Cup. He made his Leicester debut on 23 August against Everton, scoring once in a 2–0 victory. His goals ratio helped him to compete with Derek Hines for the centre forward position. He scored in every round of the 1960–61 FA Cup competition to help Leicester reach the final. However, after Leek's celebrations after the semi-final victory, manager Matt Gillies dropped his striker and replaced him with Hughie McIlmoyle for the final, which Leicester lost 2–0 to Tottenham Hotspur. He left Leicester just weeks later, having scored 43 goals in 108 appearances, with 34 of those coming in 93 league matches. In the summer of 1961 he played with Montreal Concordia in the International Soccer League, and National Soccer League.