Mian Shahid was arrested by police in Ireland at about 22:40 local time on Monday as he boarded a flight to Dubai.
The Irish state broadcaster RTÃ‰ reports that he is being detained at Clontarf Garda Station and is expected to appear at a special sitting of the High Court in Dublin later.
His arrest followed the receipt of a European arrest warrant.
Earlier this year, it is thought that Shahid travelled to Ireland from Scotland, where he had lived temporarily.
He was last seen in the Foynes areas of Limerick on 11 August.
Police in the Republic of Ireland had appealed to the public for assistance last Thursday after a search for Shahid proved unsuccessful.
The 19-year-old, who is originally from Pakistan, was convicted (in his absence) at Stafford Crown Court on 13 April, of two counts of sexual assault, and a warrant was issued for his arrest the next day.
He was sentenced to 30 months imprisonment on 20 May, also in his absence.
A convicted sex offender who was wanted by police in the UK has been arrested at Dublin Airport.