There were 1,100 births to teenage mums in 2012.
Teen birth numbers in other parts of the UK and Ireland were also down.
The drop in Northern Ireland was not down to more women from the region going to Great Britain for abortions, NISRA said.
Rates of teen births decreased right across Northern Ireland, in deprived communities as well as more affluent ones, it stated.
A total of 25,300 live births were registered last year, half of which were to mothers aged 30 or more.
Around 10% of the new arrivals were delivered to mothers, who hailed from outside the UK and Ireland.
Forty three per cent of births were to unmarried parents - the highest figure ever.
The latest figures were released on Wednesday by the Statistics and Research Agency (NISRA).
David Marshall, from NISRA, said: "In overall terms the number of births has remained broadly stable over the last five years.
"However, the number of births to older mothers continues to rise and the number to younger mothers, especially teenage mothers, falls.
"These demographic changes will have an impact on society and future public policy."
Audrey Simpson, director of the Family Planning Association (FPA) in NI, said: "I think we in Northern Ireland have been very innovative in the way we work with young people.
"I think that the initiatives we have been doing has been a long game and we are beginning to see the fruits of that."
She said there were good community-based programmes and teachers were being trained by the Public Health Agency
"What we don't want is someone in the Department of Health thinking we have cracked this," she said.
"We could be doing better with more sustainable funding."