Chapman became Arsenal manager. Needing a new centre-forward, he signed Lambert for £2,000 in June 1926. He made 16 appearances in his first season with the club, but only scored one goal. He also made 16 appearances in the 1927–28 season, but managed to score three times. He became a regular for the club towards the end of the 1929–30 season, during which he scored 18 times in only 20 league appearances, and was also prolific in that season's FA Cup. His four goals in six appearances helped Arsenal reach the final, in which they beat Huddersfield Town with goals from Alex James and from Lambert himself. He played in Arsenal's 2–1 victory over Sheffield Wednesday in the FA Charity Shield at Stamford Bridge in October 1930.