Gardaí are to conduct a full review of the case of Sophie Toscan du Plantier.
The French filmmaker was beaten to death with a brick and a rock outside her holiday home in Schull in west Cork, two days before Christmas in 1996.
An Garda Síochána say the investigation into her murder "has remained active and ongoing."
It says: "Following a review by Assistant Commissioner, Organised and Serious Crime, the Garda Serious Crime Review Team will now conduct a full review of this case."
It adds that once this review's finalised, the Serious Crime Review Team will provide recommendations to the local investigation team.
Gardaí are also continuing to appeal for anyone with information to come forward.
The force is asking people to contact the investigation team at Bantry Garda station on 027-208-60 or the Garda Confidential Line at 1800-666-111.