External overnight trips went up by 5%, reaching 2.3 million, due to a large influx of British people.
However, tourism numbers from the Republic of Ireland continue on a deep downward spiral.
In 2015 they slumped by 18% on the previous year, with the problem now being looked at by a "recovery task force" at Tourism Northern Ireland.
Overnight trips by visitors from across the border totalled 320,000 in 2015, while in 2012 there were 430,000 overnight trips made.
In 2014 a report for Stormont said an "image problem" may explain the fall, but the weakness of the Euro last year will not have helped.
The Department for the Economy's new statistics show that the Giant's Causeway remains the most popular visitor attraction.
In 2015 it had over 815,000 visitors.

Kent Police said the man, from West Sussex, sustained a serious injury when his Ford Focus came off the road in Hoath Way on Friday.
He was taken to Medway Maritime Hospital but died on Saturday evening.
Police said the car left the carriageway before mounting a grass verge and overturning. No other vehicles were involved.
It is not yet known why the man lost control of his car.
Visitor numbers to Northern Ireland hit an all-time high in 2015, according to new tourism statistics.
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A 67-year-old driver has died in hospital after he crashed his car in Gillingham.