The current layout of the ramp to platforms 8-11 acts a bottleneck resulting in an uncomfortable experience for passengers.
The £11.7m investment will see the access widened allowing more space for passengers to move from the concourse to their train.
The work coincides with other Euston station upgrades due in 2021, including new information screens and improvements to the announcement system.
The platform access improvements will start this Christmas and are expected to last until summer 2021.
During the work there will be no disruption to passengers.
Joe Hendry, station manager at London Euston said: “Over the last couple of years, passengers will have seen Euston in various states of construction as we’ve worked to improve our facilities and pave the way for HS2.
“Though we can’t make the station building bigger, this work will help us get passengers to where they need to be more effectively and efficiently. I’m confident our ongoing work to improve information systems, signage, widening the concourse and access to platforms, along with better facilities and retail offering, will make journeys through the station much smoother, easier and pleasant.
“I really care about our passengers and I’ve listened to what they have to say. I’ve been using the feedback I’ve received through Twitter and our national helpline to help shape this project.”
As the country continues to control the spread of Covid-19, Euston station is continuing its enhanced deep cleaning programme to keep passengers safe.
Hand sanitiser stations, perspex screens in offices, on buggies and at information podiums have also been installed across the station.
Passengers are asked to follow Government guidance around the use of public transport this Christmas.