Dublin County was a parliamentary constituency represented in Dáil Éireann, the lower house of the Irish parliament or Oireachtas from 1921 to 1969.
A by-election was held to fill the seat left vacant by death of the Fianna Fáil TD Patrick Fogarty.
A by-election was held to fill the seat left vacant by death of the Fine Gael TD Batt O'Connor.
A by-election was held on 9 December 1930 to fill the seat in the 6th Dáil which had been left vacant by the death of Cumann na nGaedheal TD Bryan Cooper.
A by-election was held on 14 August 1927 to fill the seat in the 4th Dáil which had been left vacant by the assassination on 10 July of the Minister for Justice, Cumann na nGaedheal TD Kevin O'Higgins.
A by-election was held on 18 February 1926 to fill the seat in the 4th Dáil which had been vacated by the death of the Independent TD Darrell Figgis.
A by-election was held on 19 March 1924 to fill the seat in the 4th Dáil which had been left vacant by the death of the Cumann na nGaedheal TD Michael Derham.