ScotRail worked with Transport Scotland, cycling groups and outdoor specialists to work out how best to adapt the carriages to accommodate up to 20 bikes and bulky sports gear.
The three redesigned carriages have space for ordinary bikes, a limited number of tandem cycles and an e-bike charging socket, said to be unique on a train in the UK.
Alex Hynes, managing director of Scotland’s Railway, said: “This is a landmark moment for lovers of Scotland’s great outdoors.
“For the first time in the UK, a train carriage will be able to accommodate up to 20 cycles which will allow more people than ever before to enjoy the majestic scenery this country has to offer.
“It’ll also be a welcome economic boost for rural communities, many of whom depend on tourism for their livelihoods.
“I am delighted, and proud, that ScotRail is able to deliver this service, further enhancing the appeal of our world famous and iconic West Highland Line.”
The carriages will be added to a limited number of existing West Highland services to boost capacity.
Customers must book their bike’s space to guarantee its place on board.
The exterior livery of the train was designed by Scottish artist Peter McDermott and features images of typical Highland scenery along with some of the best-known visible landmarks along the West Highland Line, including the Glenfinnan monument and viaduct, Ben Lomond, and the castle on Loch Awe.
Transport Minister Graeme Dey said: “The launch of this service marks a real step forward in encouraging an active lifestyle and tourism opportunities.
“By offering so many cycles spaces on board trains which serve some of Scotland’s most scenic routes, we can help even more people get out of cars and into the great outdoors.
“At the same time, we are opening economic opportunities for local communities working hard to recover from the impacts of the pandemic.
“I’m sure cyclists and adventurers from across Scotland and beyond will look forward to using this unique service.”
The West Highland Line was chosen for the initial launch because of the access it provides to the rest of Scotland.
Starting in Glasgow, the line takes passengers past Loch Lomond and on to Oban, from where they can travel to many islands.
The carriages were modified by Brodie Engineering in Kilmarnock.
Grace Martin, Scotland director at Sustrans, a charity which aims to make it easier for people to walk and cycle, said: “The carriages are a great example of how we can work together to make walking, cycling and public transport more attractive and convenient options, giving people the opportunities to make more of their journeys without the need for a car.”