The latest homeless figures show a monthly drop of 717 people - more than three times the reduction seen in the same period the previous year.
There were 9,731 people in emergency accommodation in December, compared to 10,448 in the previous month. It is the largest recorded monthly drop.
Housing officials had been expecting a reduction, but the figures - from the Department of Housing, Planning and Local Government - have come as a surprise.
There is usually a seasonal decrease in homeless figures in December, but this is more than three times the reduction of 215 seen in December 2018.
It is the biggest drop ever recorded in the homeless statistics, and it is the first time in recent years that there has been a year-on-year decrease.
The Peter McVerry Trust has welcomed the news, and said they are hopeful that the trend will continue given the improvement in housing supply.
Department of Housing officials said the decrease in homeless numbers can be explained by housing units being completed in the final quarter of 2019, with a 49% increase in local authority housing last year.
In 2019, 28,000 social housing units were provided with 10,000 of these being new social housing stock, comprising new builds, purchases and leasing.
Brendan Kenny, Assistant Chief Executive of Dublin City Council, said he is hopeful that the spike in homelessness associated with January and February can be avoided.
He pointed to the national figures showing 6,900 social housing units under construction.