Pearson started his career with Hull City. As a young player and replacement for local hero Chris Chilton he was not given an easy time by the Hull City fans. He did, however, soon win them over with skill and clinical finishing. During his time at Hull City his efforts, on one occasion, earned him the memorable headline "Onion Stu Lands City In A Pickle": this headline came about after Pearson was sent off against Sheffield Wednesday for calling the linesman "a bloody onion". City lost that game at Hillsborough 4–2 with Pearson having scored both Hull goals before his dismissal. He later joined Manchester United in 1974 for £200,000.
Pearson was bought by Manchester United after they were relegated to the Second Division and was instrumental in getting the club promoted back to the First Division the very next season by scoring 17 goals. Every time he scored a goal he would celebrate with an upraised right fist. He was in the team that lost 1–0 to Southampton in the 1976 FA Cup Final. The next year Pearson helped Manchester United win the 1977 FA Cup Final against Liverpool, scoring the first of Manchester United's goals in their 2–1 win. He was sidelined for most of the 1978–79 season due to a knee injury but made a full recovery before leaving Manchester United for West Ham United in August 1979.
He helped the Hammers win the 1980 FA Cup Final, with his cross-shot setting up Trevor Brooking for the only goal in a 1–0 win over Arsenal. Pearson retired from league football in 1982 due to a knee injury, but continued to play at a lower level, in South Africa and the NASL.