Defence Minister Alan Shatter confirmed he had secured Dáil approval for the deployment of 440 soldiers to the UN-mandated force in the Middle East.
About 90 troops will depart on May 23 to set up the base camp in southern Lebanon for the main contingent, to be deployed towards the end of June.
Mr Shatter said: “It is vitally important for Ireland to maintain a level of commitment to international peacekeeping operations and the obligations it has assumed through its membership of the UN. Overseas operations contribute greatly also to the professional development of the Defence Forces.”
The Irish area of operations will measure some 140km sq extending in the Hezbollah-controlled country from Tibnin to the border with Israel.
Their role will involve the protection of civilians, extensive mobile patrolling throughout the Irish area of operations, and monitoring along the blue line.
Irish officers were first sent to Lebanon as observers in 1958, with the first battalion sent as part of the United Nations Interim Force in Lebanon (UNIFIL) in 1978 formed after Israeli troops occupied the region.
A total of 47 Irish troops have lost their lives in the cause of peace in Lebanon.
The main Defence Forces battalion was withdrawn in 2001 following 23 years of service but were deployed again in 2006.
This deployment will be initially for 12 months, subject to renewal, and Ireland’s participation will not exceed a maximum of three to four years.
Mr Shatter said the Dáil vote completed the triple-lock mechanism of UN, Government and Dáil approval before deploying members of the Defence Forces overseas.
“Ireland’s participation in UNIFIL is an illustration of the very positive and practical difference that small countries like Ireland can make in the world’s trouble spots by supporting the United Nations,” he said.
There are currently 131 Defence Forces personnel serving overseas in 13 mission areas or headquarters.
Another 150 personnel are on stand-by for short-notice deployments as part of the EU Nordic Battle Group.