Almost 7,000 people were classed as homeless on census night last year.
The latest report from the 2016 population count revealed homeless people were on average younger and sicker.
The Central Statistics Office (CSO) said about one-fifth of people who were recorded in emergency or temporary accommodation indicated their health was fair, bad or very bad, almost double the rate of the general population.
The disability rate among the homeless was double that of the general population, the CSO said, with 1,871 people indicating they had a disability.
It also revealed that about one-third of the 2,915 homeless people in the labour force were working.
The CSO said its homeless numbers were based on where people were living on census night April 24 2016 and not through self-identification.
Some 2,887 people were recorded in private emergency accommodation; another 2,681 were in supported temporary accommodation; and another 1,144 people were in temporary emergency accommodation.
The headcount also found 123 rough sleepers, 102 of whom were in Dublin.
The CSO said it did not include the 1,772 people in l ong-term accommodation in its report on homelessness as they were classed as tenants even though they were receiving specific supports.
Senior statistician Deirdre Cullen said: "This report will help to further improve our understanding of this complex issue, by providing important new information on the social and economic circumstances of homeless persons.
"The collection of data in this important area could not have been achieved without the input and assistance of a broad range of both government and non-government stakeholders, and the CSO would like to thank all concerned for their cooperation in this."
A breakdown of the census records on homelessness found 6,906 people were either sleeping rough or in special accommodation for people without a home, including 4,018 males and 2,888 females.
The average age of a homeless person was 31.
Some 1,846 homeless people were aged 17 or under, including 1,594 children in family units. Another 413 people were aged 60 and over.
There were 896 families classed as homeless on census night, including 111 families with four or more children.
There were also 567 one-parent families, with the vast majority mothers.
The CSO also noted that 429 students were homeless.
Focus Ireland said the most shocking revelation was the huge number of children under four who are homeless - 765.
But the charity's director of advocacy Mike Allen said: "This census data also demolishes many of the myths that people have about 'the homeless'.
"It shows that people who are homeless look very much like everyone else in the population. This demonstrates the extent to which homelessness is linked to the wider housing crisis that impacts on all sections of society."
Focus Ireland also noted the growth in the number of Travellers who are homeless - 163 in 2011 to 517 last year.