At the 1937 general election, he was elected as a Fine Gael TD for the Galway West constituency. He was re-elected at each subsequent general election and served until his death in 1951. No by-election was held for his seat.
References
^"Joseph Mongan". Oireachtas Members Database. Retrieved 18 January 2009.
^"Joseph Mongan". ElectionsIreland.org. Retrieved 18 January 2009.