The Jacobite steam train, which featured in the film series, offers seasonal trips between Fort William and Malliag, Scottish Highlands.
But was forced to operate a reduced capacity this year – running with just a third of its normal passengers due to new guidelines on social distancing.
Rail bosses have now said the popular service will run a morning and an afternoon service seven days a week for its entire seven-month season next year.
In previous years the train has run from Monday to Saturday, but demand for seats will see it also operate on Sundays from Easter until the end of October next year.
The 84-mile round-trip travels past some of Scotland's most treasured sights – including Ben Nevis and crosses the Glenfinnan viaduct, which features in the JK Rowling films.
A spokesman for West Coast Railways said: “Unfortunately Covid-19 did last year what Harry Potter's arch enemy Lord Voldemort couldn't – and temporarily derailed the Hogwarts Express.
“We realise this left a lot of people disappointed at not being able to travel on the Jacobite, which has been voted the greatest train journey in the world.
“So next year it will be full steam ahead as we plan, for the first time, to run a seven-day-a-week service throughout the season.
“For much of that time there will be two trains a day – one in the morning and the other in the afternoon.”