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.
Mr Hill had said the pair were setting up camp in the Wonnangatta Valley, near a camping ground in the Victorian Alpine National Park.
Passers-by found their campsite destroyed by fire the next day, but police were not notified until later that week. Campers noticed that Mr Hill's car, parked nearby, also bore signs of fire damage.
Police have conducted several extensive searches, looking for clues in the rugged terrain.
The investigation has picked up in recent months. Authorities released pictures of a 4x4 car that had been spotted near the pair's campsite at the time, saying they wished to speak to the driver.
The families of the missing pair have also issued appeals for information.
"It's really hard. It's not getting any better not knowing. It's just unknown - he just disappeared and you're just stuck in the middle," said Mr Hill's daughter, Debbie, last month.
Ms Clay's sister, Jill, said: "We need to know what happened and we need to know where their bodies are so we can put them to rest."
Three other people have gone missing in the Victorian Alps in the past decade, but none are suspected to have met with foul play.
Mr Hill knew the area well from frequent visits and work decades ago as a logger, local media reported.