Official figures for the year to September 2014 showed spending rose by 3% to £756m with trip numbers up 2% to 4.3m.
However, when trips and spending by NI residents were stripped out there was no significant growth.
Spending by non-NI residents actually slipped slightly from £521m to £519m over the year.
The Stormont Executive has targeted tourism as a growth industry that should be delivering £1bn a year to the economy by 2020.
The numbers of trips and spending has been on an upward trend since 2011.
The overall rise in the year to September was driven by a 21% increase in the number of people taking holidays in Northern Ireland, rather than visiting relatives or making business trips.
The figures also showed a continuing trend of a growing number of visitors from outside the UK, but a steep fall in total visitors from the Republic of Ireland.
Total overnight trips from Great Britain and other countries was up 3% but overnight trips from the Republic of Ireland were down by 13%.
Northern Ireland's tourism industry saw a rise in visitors and spending during the period that covered last summer.