Donnelly played as a forward or wide midfielder for Queen's Park, Celtic, Sheffield Wednesday, St Johnstone, Dunfermline Athletic, Partick Thistle and Scotland.

He failed to improve on this tally in the following season as he did not score in 17 outings, although the team reached both domestic cup finals, and he was part of Celtic's Scottish Cup-winning side.

[7] Joining Coventry City on trial,[8] Donnelly instead returned to Scotland with St Johnstone, signing a one-year deal in August 2003.

However, following the departure of Partick coach John Henry to Burnley, Donnelly rejoined the Jags as a player-coach, scoring against Morton in a 2–0 win at Cappielow later that season.

The following season Donnelly also featured regularly for Scotland, playing in a number of friendlies ahead of the 1998 World Cup,[5] although he failed to make an appearance during the tournament.

[17][5] In September 2020, Donnelly landed the assistant manager's job at Scottish side Brechin City, working with another former Celtic player, Mark Wilson.

[20] His father Tom Donnelly was also a footballer, who failed to break into the team at Rangers[21] in the late 1960s but played for Motherwell and East Stirlingshire over the next decade before becoming a school teacher.