Leicester born outside left Tommy Allsopp played in the Football League for Second Division Leicester Fosse, joining them in 1900 and making his Football League debut at Middlesbrough in February 1901. After 3 goals in 34 appearances he joined Southern League Luton Town in 1902, before rejoining Leicester in 1904 and playing a further 36 matches, scoring 5 goals, in the 1904-05 season. He then joined Southern League Brighton & Hove Albion in the summer of 1905, and moved to Norwich City in 1907, where he finished his football career in 1911 for whom he scored 27 goals in 132 appearances..
He also played First Class cricket for Leicestershire County Cricket Club and Marylebone Cricket Club, playing 37 times for Leicestershire, scoring 347 runs and taking 88 wickets. His highest score of 32 came when playing for Leicestershire in the match against Hampshire and his best bowling of 6-85 came when playing for Leicestershire in the match against London County. He also played 27 Minor Counties Championship games for Norfolk between 1907 and 1912. On his Norfolk debut against the Free Foresters he took seven wickets and then hit a half century in his third innings against Harrow Wanderers.He also played two matches for Norfolk against Essex Second XI team. His best season was in 1910 when he helped Norfolk win the Minor Counties Championship. His highest score was 69 not out in a match against Bedfordshire.
After retiring from football, Allsopp took ownership of the Hero of Redan pub in Thorpe Road, Norwich in May 1911. He served as a sergeant in the Queen’s Royal Regiment (West Surrey) and the 126th Labour Corps during the First World War. During his return home from the War, he fell victim to the 1918 flu pandemic and died in Norwich on 7th March 1919. He was buried with military honours in Earlham Road Cemetery, Norwich.