Philip Cassidy competed in the 100 kilometres team time trial at the 1984 Los Angeles Olympic Games, replacing Paul Kimmage who had ridden the road race.

The Irish team finished 16th, over 12 minutes behind the remarkable Italian team who rode the fastest 100 kilometres in Olympic history using solid front and back carbon-fibre disc-wheels.

Cassidy had won the 1983 Rás Tailteann and rode the French amateur circuit in 1984 with the Parisian club US Creteil. He also competed at the Seoul 1988 Olympics as part of the Irish cycling team.