There was a 13% increase in outbound travel in 2016
The Department of Foreign Affairs is hiring over 200 new staff as a result of the Brexit referendum in Britain.
Irish citizens, irrespective of where they live, are entitled to carry Irish passports.
In a statement, the department says: "While we do not compile information on why citizens apply for passports, it is reasonable to assume, based on the trends in applications from Northern Ireland and Great Britain, that the outcome of the UK referendum on EU membership is one of the factors that has led to an increase in demand."
Figures so far this year show an increase of over 77% in Irish passport applications in Northern Ireland, and a near 71% increase in Great Britain.
Other factors are said to include a 13% increase in outbound travel in 2016 - compared to the previous year.
While a large contingent of Irish citizens travelling overseas for the Euros, and a spike in applications in 2006 feeding through in renewals ten years later, are also being singled out.
The Foreign Affairs Minister Charlie Flanagan added: "Early indicators in 2017 are showing that increased demand for passports is likely to be sustained, certainly in the immediate future.
"We are in the course of delivering a major Passport Reform Programme which will ensure significant customer service improvements to benefit citizens in the near future.
"This includes the introduction of online adult renewals which will mean a more efficient service for applicants. I expect to start rolling out this programme before the end of March this year."
The Passport Service is recruiting more than 230 temporary clerical officers, over half of which are already in place.