The Disney store has donated the 2,000 soft toys that comprise the Disney Junior Christmas Tree, which is said to be the largest of its kind in the world.
A one-metre high Mickey Mouse toy sits on top of the tree, along with characters from shows such as Doc McStuffins, Sofia the First and Miles From Tomorrow.
To add to the experience, artificial snowflakes fall from the tree every four minutes, and they dissolve as they reach the ground.
The tree is designed to bring Disney Junior’s motto ‘Where the magic begins’ to life, and will be hosting a series of events, including a Frozen sing-a-long in association with Yamaha.
When the tree is dismantled on 4 January, the toys the tree will be donated to children’s charity, Kids.
David Levine, general manager, Disney Channels UK & Ireland, said: "Christmas is always a magical time at Disney Junior and this year we wanted to bring the holidays to life for people of all ages.
"St Pancras is not only one of the busiest stations in the county, it’s also one of the most beautiful. We couldn’t think of a better setting to house our magnificent soft toy creation, which will be surprising and delighting families over the next two months. We’re also thrilled to partner with a fantastic charity like Kids to ensure that these toys find loving homes after the last snowflake has fallen."
Nicola Shaw, chief executive of HS1 - owners of St Pancras International - added: "The Christmas tree in St Pancras stands at the heart of our station and over the years has itself become a destination for visitors during the festive period. St Pancras has housed unique creations that have each articulated the joy of Christmas in their own way.
"This year’s Disney Junior soft toy tree, with its 2,000 characters and falling snow inside the station for the first time is perhaps our most extraordinary and magical yet."