Meanwhile, 100 students, teachers and parents are sleeping out for two nights to raise funds for charities
Focus Ireland says it has helped 14,500 people who were homeless or at risk of homelessness this year.
The figures mark a 7% increase compared to 2016.
According to the charity, it has worked with the State to support 720 families - including more than 1,500 children - in securing a home and escaping homelessness.
In a Christmas message, Focus Ireland founder Sr Stan said: "There are over 3,300 children who are still homeless and we need to make sure they are all in homes as soon as possible.
“It breaks my heart to know that some of these children have been born into homelessness. Some of them will now spend their first Christmas stuck with their family forced to live in one little room together."
Meanwhile, more than a hundred students, teachers & parents are gearing up for their second night on the streets of Dublin to create awareness about homelessness.
The pupils from Belvedere College are collecting money for three charities (Home Again, the Peter McVerry Trust, and Focus Ireland) and are hoping to raise over €225,000.
Halfway through #SleepOut17 and spirits are high. Pop down to the GPO to support the lads or drop some change into their buckets around town. Help support us this Christmas!! Donate @ https://t.co/LAS9Z3JBjz #SleepOut17 pic.twitter.com/7mDkO0kkip— Belvedere Sleep-Out (@belvosleepout) December 23, 2017
Student Cathal McGuinness described what the first night was like.
He said: "It wasn't as cold as we thought. We didn't get much sleep, but that's kind of expected - there's still a lot of foot traffic, a lot of people passing by, and a lot of buses still going up. But we managed to survive."
He added: "We're not trying to replicate homeless - all we're trying to do is raise awareness, and raise money for the three homeless charities."