Police say they have caught two men with more than $2.5 million in their suitcases at Sydney's Central Railway Station.

Officers arrested the pair on the Indian Pacific train from Perth late on Saturday morning after a tip-off from another passenger in Western Australia.

Police say when the searched the pair's baggage they allegedly found the money, mostly in $50 notes.

The men, from Auburn and central Sydney and both in their mid 20s, have been released on bail to face court next month on charges of dealing in the proceeds of crime.

Acting Inspector Alex Liouthakis says police have no idea where the money came from.

"The police case will hinge on the, I guess let's call it the unexplainability of why somebody would have that enormous amount of money, yet not have a reasonable explanation as to where it came from," he said.

"We would appeal to any members of the public who either know these gentlemen or have some information as to the origin of the cash to come forward."

Anyone with information should call Crime Stoppers on 1800 333 000.