Transport Minister Keith Brown unveiled the new facilities at Edinburgh's Haymarket station today.
Network Rail said the project, delivered on time and on budget, offers more shops and a public space 10 times larger than before.
The steel and glass building also links to all platforms via a new footbridge with lifts and escalators.
Alex Sharkey, Network Rail's area director for the east of Scotland, said: "Haymarket station is already one of the busiest in Scotland and passenger numbers are set to continue to grow in the years ahead.
"This new building will ensure the railway is able to provide first-class facilities for those passengers and the new, modern station will also complement the wider redevelopment of the city's west end."
The work at Haymarket began in 2012 and the full refurbishment is set to be completed by the spring of next year.
Passenger numbers at the station are expected to climb from the current four million a year to 10 million by 2030.
The work has been completed as part of the Scottish Government-funded Edinburgh-Glasgow Improvement Programme (EGIP), which is delivering a rolling programme of electrification across the central belt, aimed at reducing journey times and boosting capacity on routes.
Mr Brown said: "The exciting £25 million redevelopment of Haymarket Station marks a hugely important milestone in the Edinburgh-Glasgow Improvement Programme and I am delighted to be able to unveil the station's stunning new look to the public.
"Network Rail and ScotRail have worked extremely well together to deliver this transformation of one of our most iconic stations on time and on budget and I look forward to seeing this kind of successful collaborative approach continue throughout EGIP."
ScotRail's managing director Steve Montgomery said the revamp will encourage even more people to travel by train.
He said: "More than 22 million journeys a year are already made to and from Edinburgh on ScotRail trains. That's more than a quarter of our overall record breaking passenger numbers. The new Haymarket is a real boost for Edinburgh - and beyond, and I have no doubt the growth will continue."