He won an FAI Cup winners medal and League of Ireland title with Shamrock Rovers and Shelbourne respectively.
He made his debut for Wednesday on 19 March 1938 in a 1–0 home defeat to Barnsley, playing in all ten of the remaining League games of that 1937–38 season.
He formed an exciting left wing partnership with Charlie Napier in the 1938–39 season, appearing in 40 matches in all competitions, scoring 11 goals as Wednesday missed out on promotion from the Second Division to city rivals Sheffield United by one point.
[6] One of Fallon's best displays for Wednesday was against Norwich City in November 1938 when he teased and tormented the Canaries' defence in a 7–0 win.
[7] Fallon had a lucky escape just before Christmas 1938 when the car he was travelling in, together with fellow Wednesday player Ted Catlin, skidded in snow at Wadsley Bridge and hit a telegraph pole.
[8] On 2 September 1939 Fallon appeared in the final Sheffield Wednesday match before the outbreak of the Second World War against Plymouth Argyle.
After the war Fallon returned to Wednesday, but he did not figure in their plans and was given a free transfer back to Notts County in June 1946.
Following the outbreak of the Second World War, Fallon returned to Ireland where he joined the Irish Army and played for three different clubs – Shamrock Rovers, Shelbourne and Dundalk.
Among his teammates at City was his younger brother, Peter Fallon, who also played for Notts County and Queens Park Rangers in the 1940s.
His career ended when he suffered a broken collar bone playing for Peterborough reserves against Notts County.