The Peter McVerry Trust has said hundreds of workers are giving up their own family time to support the homeless on Christmas Day.
CEO Pat Doyle has said more than 200 staff will also be separated from family on December 25th as they work to help others.
He told Newstalk Breakfast this time of year can be triggering for some people.
"It's busier than ever... there's more people in homeless services than ever before," he said.
"We'll be open 24 hours a day, right throughout the Christmas.
"That involves making sure that everybody's minded, first of all - it can be a very sad time for people in homeless services - especially anybody who's suffered trauma in care or anything like that.
"Christmas can be a real trigger.
"We have to mind everybody, mind their mood, mind the fact that they get something under the tree, that they're not feeling too alone and isolated".
Presents from Santa
Mr Doyle said the charity must think about the logistics of that as well.
"We'll be providing services for over 3,000 people on Christmas Day,” he said.
"We'll be directly providing meals for over 1,000; we have 300 Christmas trees up across our services to try to make it feel and look like Christmas.
"There'll be 250 staff separated from their families on Christmas Day, either volunteered to work or rostered on to work for Christmas."
He said Santa will be coming to children in their services as well.
"In our family services we'll have 317 children getting presents from Santa under the tree," he said.
"Anyone living in our family hubs across Dublin, Galway, Meath, Louth or Kildare - those kids will be celebrating Santa.
"We run services for children in care, so we'll have 47 kids with us on Christmas who have been taken into care for their own safety.
"They have to have a Christmas, and they have to have Santa and they have to have their clothes, and they have to have all the things that your children or my children may have".
'All the trimmings'
He said while people will enjoy the day, it is hard not to think about what happens next.
"None of that can compensate from being separated from family, or not knowing where you're going to live next year," he said.
"You're kind of managing all that mood, energy and tension and sadness that's going on under the surface at the same time.
"It'll look and feel, I hope, as much like home.
"All the trimmings, all the trees, all the crackers, all the Chocolate Kimberley - whatever it might be - we'll do our best.
"We couldn't do that without your listeners and without the support of the public," he added.