The Taoiseach, members of the cabinet and representatives of the diplomatic core gathered at the US embassy for a special September 11 commemoration.
One minute of silence was observed in the Embassy at 1.46pm. The Stars and Stripes are flying at half-mast in front of the Embassy.
Among those that performed at the ceremony were the Kilkenny Gospel choir and the Army No 1 band. The Garda Siochana, the Dublin Fire Brigade and American Legions all laid wreaths as piper David Byrne of Tara St Fire Station played an appropriate lament.
It is estimated that 500 people of Irish extraction lost their lives in the attacks.
The ceremony ended just before 2pm.