Irish-based international aid agency GOAL said that 27 of its colleagues are confirmed dead in the earthquakes which struck Turkey and Syria this week.
It said that teams are working around the clock to trace a number of staff who are still unaccounted for, while also supporting the overall search and rescue mission.
In a statement, GOAL said that never in its history has it experienced the loss of colleagues on such a scale.
It said that GOAL staff across the region have also lost family members, sustained life-altering injuries and lost their homes.
Twenty-six Syrian citizens and one Turkish citizen who worked for GOAL died in the quakes.
Tánaiste and Minister for Foreign Affairs Micheál Martin said he was "was deeply saddened to hear of the significant loss of life among GOAL staff".
He said: "The staff members who died dedicated their lives to supporting people in need of humanitarian care. Each of them leaves a legacy of kindness, compassion and humanity."
A Turkish official said the disaster posed "very serious difficulties" for the holding of an election scheduled for 14 May in which President Tayyip Erdogan has been expected to face his toughest challenge in two decades in power.
With anger simmering over delays in the delivery of aid and getting the rescue effort under way, the disaster is likely to play into the vote if it goes ahead.
The first UN convoy carrying aid to stricken Syrians crossed over the border from Turkey.
In Syria's Idlib province, Munira Mohammad, a mother-of-four who fled Aleppo after the quake, said: "It is all children here, and we need heating and supplies. Last night we couldn't sleep because it was so cold. It is very bad."
Meanwhile, Concern Worldwide's Chief Executive David Regan expressed his condolences on behalf of the humanitarian organisation to the family and colleagues of GOAL global staff who died.
In a statement, Mr Regan said: "On behalf of all of us at Concern, we are very sorry to hear that staff from GOAL lost their lives after the earthquakes in Turkey and Syria.
"Our thoughts and sympathies are with their families, friends and colleagues at this devastating time and with all our partner organisations who have lost staff during this ongoing humanitarian emergency."
