The report found a 17% decrease in butterfly abundance and a 10% decrease in butterfly distribution across the six counties.
The country’s population of the Wall butterfly is dying out, according to the report, while another species, named the Small Heath, has lost 40% of its distribution since 1995.
More positively, the Cryptic Wood White, which is endemic to Northern Ireland, has increased in numbers, as have the Silver-washed Fritillary, Dark-green Fritillary, and Holly Blue species.
"We need swift and effective action on this," said Julie Williams, chief executive of Butterfly Conservation.
"The decline in butterflies we have seen in our own lifetimes is shocking and we can no longer stand by and watch the UK's biodiversity be destroyed."