Dalry, Ayrshire born centre forward Jimmy Cassidy started his football career at his local club Kilmarnock Athletic in 1886, joining Kilmarnock in 1887 before a very unpopular move to the short-lived Glasgow Hibernian in 1888. In 1889, he joined Bolton Wanderers making his Football League debut that November at West Bromwich Albion, and in an explosive debut season he grabbed 20 goals in 19 appearances, scoring 4 goals against Derby County in a 7-1 win at the end of the same month and 5 goals in a 13-0 FA Cup thrashing of Sheffield United in February 1900. A week later he scored a hat-trick in a 5-0 win over Stoke, His only other career hat-trick came against Aston Villa in a 5-0 win in September 1892,
He remained with The Trotters for nine seasons, making 219 appearances, scoring 101 goals, a great figure even for those early days. He was said to have had a great shot, and cracked a post at Molineux in December 1889. Cassidy scored Bolton’s consolation goal in the 1894 FA Cup Final, when they were beaten by Notts County at Goodison Park.
He had 2 loan spells while at Burnden Park. In 1890 he was loaned to Carfin Shamrock and then Cassidy played a single match for Glasgow Celtic in May 1892, his appearance apparently said to have added thousands to the gate of a humdrum League fixture against Leith Athletic in a 2-0 Celtic win. He returned to play for Bolton and was a regular scorer through to the end of the 1897-98 season, when after nine seasons at Bolton he joined Wigan County in the summer of 1898 before his eventual retirement.