Bradford born inside forward Harry Dennison was playing junior football for Blackburn Trinity before signing for First Division Blackburn Rovers in January 1911. He made his Football League debut, and only appearance of the season, that April against Bristol City and repeated his single appearance in April the following season as Rovers won the League Championship. However due to the First World War he didn’t play again for Rovers’ first team, again a solitary game at Bradford City, until November 1919 some seven and a half years since his previous outing against Newcastle United.
Before the year end he had joined (then non league) Accrington Stanley and moved to Rochdale in June 1920, and when ‘Dale joined the Football League in August 1921, Dennison played in their inaugural match against former club Accrington Stanley. He played 34 games that season scoring 18 goals finishing comfortably the club’s top scorer, moving to Wigan Borough in June 1922 where he scored 4 goals on his Borough debut in a 6-1 win over Ashington that August. His 14 goals in 35 appearances again saw him top the club’s goalscoring chart, before he joined non league Stalybridge Celtic at the end of the season in the summer of 1923. In May 1924 he joined Second Division Stockport County and scored 3 goals in 11 appearances that autumn including a debut goal against Stoke followed immediately by a goal against Manchester United, before returning to non league Stalybridge, playing for them for a further three seasons.
In 1928 he joined Hurst, but moved to Macclesfield Town that November, where he played fairly regularly for The Silkmen throughout the remainder of the season at either centre forward or inside left, scoring 7 goals in 20 appearances for the club. He joined Barnoldswick Town in 1929 and played for Lytham later the same year before returning to Stalybridge Celtic for a third time in 1930, where he finished his career.