Some PSNI officers can apply for Garda jobs
Some PSNI officers will now be able to compete for promotion to senior ranks within the Garda Siochana.
The Irish government has introduced regulations which will allow officers at the rank of inspector or above to compete for appointments.
Similar arrangements are in place within the PSNI.
The new regulations do not apply to the posts of Garda commissioner or deputy commissioner, which are at discretion of the Irish government.
Minister for Justice, Alan Shatter said the regulations were part of a commitment in the intergovernmental agreement on police co-operation.
"That agreement, which has been progressively implemented, provided that members of the PSNI or the Garda should be able to apply for positions at ranks above inspector level in the other police force."
The regulations allow members of the PSNI at the rank of inspector or above to compete for appointment in the same competition as similar ranks in the Garda, to the ranks of superintendent, chief superintendent or assistant commissioner in the Irish police.
"The agreement also provided for cooperation between the two police forces at the level of exchanges without police powers and secondment with police powers," Mr Shatter said.
"The experience gained by officers from both sides continues to enhance the level of cooperation and exchange of information between both forces.
"These new regulations mark a truly historic further step in relations between the two forces, to the benefit of policing on this island."
The new regulations come into force immediately.