Fintan Warfield is the first candidate elected to the new Seanad after topping the poll on the Cultural and Educational panel.
Mr Warfield, currently a Sinn Féin councillor for Templeogue-Terenure in Dublin, was elected on the first count.
Fianna Fáil's Dr Keith Swanick and Fine Gael’s Kieran O’Donnell were also elected in later counts, which were continuing into the early hours.
Over 1,140 envelopes have been returned for all the vocational panels, which will determine 43 senators out of 60 in the Seanad.
The electorate is made up of TDs, outgoing Senators and councillors.
Counting for the six university panel seats gets under way tomorrow.
The Taoiseach will appoint an additional 11 senators once the next government is formed.