[2] At the outbreak of the Second World War, Farrell joined the RAF and after completing his service set up a dental practice in Hull.
Farrell began his career playing junior football with Home Farm before joining Bohemians where his teammates included Fred Horlacher and Billy Jordan.
Intensive coaching corrected the problem and Farrell subsequently played a prominent role in Bohs FAI Cup run during the 1934–35 season.
When Farrell played international football between 1937 and 1938, there were in effect, two Ireland teams, chosen by two rival associations.
In May 1937 the FAI organised a European tour with a squad that included Tommy Breen, Jackie Brown and Jimmy Dunne as well as Farrell.