Her appeal comes as homeless volunteers are mourning the recent death of a homeless man on the streets of Belfast.
As a volunteer for Belfast charity The Welcome Organisation, 84-year-old Sister Olive Cooney spends her days washing clothes and sleeping bags for the homeless.
Speaking to the BBC's The Sunday News programme, she said the government could do more to help them.
"It makes me feel very very sad to think there are people out there who would have nobody to love them, to care for them," said Sr Olive.
"It touches my heart."
She explained that her hope, in washing their clothes and bedclothes, is that she might encourage the homeless to feel a sense of dignity, which could convince them to get back on their feet.
Paying tribute to homeless man Jimmy Coulter, who died earlier this month, Sr Olive described him as "a lovely person - full of life, full of beans".
Mr Coulter, who was in his mid-thirties, died in a doorway in Donegal Place in Belfast city centre.
"I was just devastated - couldn't believe it, because he came from a very good family.
"But really and truly, it doesn't matter what your family circumstances are. If you're going to go that road, you're going to go that road anyway."
The Belfast nun said she encounters "a whole range of people" on the streets, "be they in their teens, right up to quite elderly people", but that they tend to be mostly male.
"Some will come and disclose how they ended up in the street - it might be through domestic violence, domestic circumstances, addiction in the home.
"They think this is the best place for them - to just get out."
In other cases, she said, unemployment can play a part.
"And possibly foreigners coming over, looking for work and not finding it, then not having enough money to get back home."
Laughing at the affectionate comparisons to Mother Teresa, Sr Olive stressed that she was not in the same league as the revered nun, but admitted it was flattering.
"I was very humbled, because I certainly wouldn't classify myself in the same plane as our venerable, blessed Mother Theresa.
"But it gave me a sense of pride that people appreciate what I do."
Although voluntary organisations work hard to address the homeless problem in Northern Ireland, Sister Olive believes it is time for the government to step in with financial support.
"There are so many organisations out there helping the homeless. I think the government really should now up their efforts to help the homeless," she said.
You can hear Sr Olive's interview in full on The Sunday News, BBC Radio Ulster, at 13:00 on Sunday, 20 February.
A Belfast nun, known affectionately as Mother Teresa by the homeless people she helps, has added her voice to calls for more to be done to help those who sleep rough.