Russell Hill, 74, and Carol Clay, 73, were last heard from on 20 March last year when they called a friend from their remote campsite in Victoria.
Despite one of the state's largest missing person investigations, there has been no trace of the hikers since.
On Tuesday, Victoria Police said they had arrested a 55-year-old man from Melbourne in connection with the case.
He is being questioned by police but has not been charged.
Investigators believe Mr Hill and Ms Clay went missing shortly after the call to their friend using a high-frequency radio.