Maraj Karimi (15) was last seen on Sunday, September 22, 2019, in the Newton Stewart area.
The Afghan teenager is described as approximately 5 ft 4 ins tall, of slim build and has short black hair.
When last seen, he was wearing a pink/red and white polo shirt and a black bomber style jacket.
In a statement issued by Scottish Police they said:
"Police have been carrying out extensive enquiries and working with other law enforcement agencies to trace Maraj.
"We believe he travelled to Belfast in Northern Ireland by ferry around 6am on 22 September and thereafter, potentially to the Dublin area via train.
"We believe he has relatives in the Cork area and it's possible he may have travelled into the Republic of Ireland in order to reunite with his family."
The Dumfries Galloway Police Divison is appealing for members of the public to come forward if they have any information relating to the missing youth.
If anyone has seen Maraj or has any information or knowledge as to his whereabouts, they can call Police Scotland at +44 1786 289 070.