O'Donnell began his career with Motherwell F.C., making his first team debut in the 1990–91 season.

O'Donnell scored two goals in his debut for Celtic, and went on to win another Scottish Cup in 1995. He also earned his sole league winner's medal with the club in 1998, but injuries proved to be a major concern and his appearances for the club were limited.

midfielder O'Donnell returned to Scotland where former club Motherwell offered him the chance to train with them again. The Fir Park outfit re-signed him in January 2004, allowing him the chance to appear alongside his nephew, David Clarkson. He was also the uncle of St MirrenStephen O'Donnell. In his second spell at Motherwell, he was club captain.

This Saturday Phil collapsed as a result of a brain seizure during a game against Dundee United just as he was about to be substituted. He was treated on the pitch for about five minutes by the Motherwell and Dundee United club doctors before being taken by ambulance to Wishaw General Hospital. However, he was pronounced dead at 17:18. He was 35 years old and is survived by his wife and four children.