The Department of Foreign Affairs says it is working actively on the ground to resolve the case of Co Laois man Joshua Molloy, who was arrested in Iraq.
The former soldier was detained along with two British nationals in Erbil.
It is understood they had been fighting against the group known as the Islamic State (IS).
The acting Foreign Affairs Minister Charlie Flanagan says he is monitoring the situation "closely".
The 24-year-old was arrested on Friday in Erbil.
It is understood he and the two British nationals had entered the country illegally after their visas expired.
The Department of Foreign Affairs says the Irish government stands ready to provide consular assistance.
The UK Foreign Office also confirmed that they have been in contact with local authorities and that the three men are being held.
Hannah Lucinda-Smith is Turkish correspondent with The Times in Britain.
She interviewed Mr Molloy when he first arrived in Syria last year, and outlines how he came to be arrested.
"The northern Iraqi has been tightening up its policy on those foreigners going to join the Kurds in Syria", she told Newstalk Breakfast.
"They were unable to cross the border legally into northern Iraq - they were waiting for some weeks at the border trying to cross it illegally".
"When they finally did they were arrested by Iraqi security services; so they're now in a prison in Erbil, which is the capital of northern Iraq", she added.
