Detective Constables Michael Malone, 35, and Ernest Carson, 50, were killed in a gun attack at the Liverpool Bar in Donegall Quay, near the River Lagan in Belfast, on August 26, 1987.
A civilian and another officer were wounded.
The PSNI said on Wednesday: “A 54-year-old man has been arrested in Belfast as part of enquiries into the murders of two police officers in the city 29 years ago.”
Detective Inspector Stuart Griffin from Serious Crime Branch said: “The suspect is being questioned at a police station in Belfast.
“Although these murders happened a long time ago, police would continue to appeal to anyone with information about the shooting and those involved to come forward.”