He was detained by police on Friday evening in the city in connection with the illegal surveillance of gardaí based at Harcourt Street, Dublin last year.
Detectives became aware of suspicious activity in the vicinity of Harcourt Square on 26 September.
A police statement released at the time said: "A person known to them was observed at a nearby hotel. Investigations revealed that this person rented a room overlooking Harcourt Square. This room was booked in a false name."
The man was held under section 30 of the Offences Against the State Act at Ballymun Garda Station.
A file will be prepared for the Director of Public Prosecutions.
Last September, two men were arrested after cameras were found in a room of the hotel.
A 41-year-old man appeared before the Special Criminal Court while the other, aged 32, was released without charge.