The LÉ Niamh rescued 225 people from two inflatable vessels on Saturday night, 112km north east of Tripoli.
At 7.40pm, the Irish naval vessel was asked to go to the scene by the Italian Marine Rescue Co Ordination Centre (MRCC).
It deployed two rigid hull inflatable boats to the first vessel and all 107 migrants were safely on board the LÉ Niamh by midnight.
The 118 migrants on board the second vessel were rescued and on board the Irish naval vessel by 5am on Sunday morning. Weather conditions at the time were good.
The 139 men, 74 women and 12 children rescued in the operation are receiving water, food and medical assistance.
The LÉ Niamh had rescued 1772 migrants before this operation.
The Italian navy rescued a total of 1,700 migrants aboard five boats in the Mediterranean earlier on Saturday after receiving requests for help from nearly two dozen vessels, a spokesman for the coast guard said.
Europe is struggling to cope with a record influx of refugees as migrants flee war in Middle Eastern countries including Syria.
The Mediterranean has become the world’s most deadly crossing point for migrants.
More than 2,300 people have died this year in attempts to reach Europe by boat, according to the International Organisation for Migration.
On Saturday, thousands of rain-soaked migrants stormed across Macedonia’s border as police lobbed stun grenades and beat them with batons, seeking to enforce a decree to stem their flow through the Balkans to western Europe.