Marie Stopes is set to close its clinic in Belfast later this week.
The organisation says the move is in response to the UK Government's decision to provide free abortions to women from Northern Ireland in England.
Managing director Richard Bentley said: "Following the UK Government's ground-breaking move to fund abortion services for Northern Irish women using our clinics in England, we believe we can better serve Northern Irish women through our national referral service than through an independent clinic in one part of Northern Ireland.
"Therefore we have taken the difficult decision that our Belfast clinic will close in December 2017."
Marie Stopes opened its doors on Belfast's Great Victoria Street in October 2012.
Mr Bentley said for five years the Belfast team had provided services allowed within Northern Ireland’s highly restrictive legal framework.
"We are incredibly proud of all that our team has achieved in Belfast,” he said. "However, we also have to recognise that, due to the UK Government's funding announcement, the way Northern Irish women access services is changing.
"Today more than three-quarters of the Northern Irish women we see come to us directly via our national referral service. We expect this proportion to increase further now that treatment in England has been made more accessible."
He said Northern Irish law should change to give women the right to access services without having to travel to England.
And added: "Until that happens, we will continue to provide funded treatment for Northern Irish women in England - services that they should be legally granted in Northern Ireland."
The pro-life group Precious Life said it is "celebrating" the news.
Bernadette Smyth said: “When Marie Stopes opened in Belfast in 2012, Precious Life made a vow to ‘close the door’ on Marie Stopes.
"For the past five years, Precious Life has maintained a pro-life presence outside the office – sacrificing many hours in reaching out to abortion-minded women, thus saving countless lives.”
Meanwhile a statement from Alliance for Choice said it is "now time to change the law in the north and south".
Emma Campbell added: “We are so glad that the clinic operated here for five years so that women from all over the island could avail of its services.
"The clinic changed conversations and hearts and minds for that we will be eternally grateful.”