From today, an extra 18 trains will be added to the Cardiff and London Paddington timetable.
This means that the half-hourly train service between south Wales and London will return in the hope it will restore trains cut due to Covid.
Great Western Rail told the BBC the new timetable would provide communities with needed "help and support".
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The BBC reports that Great Western Rail is also starting an all-electric train service between the two stations for the first time.
Great Western Rail said this would provide a low carbon, sustainable way to supplement capacity on the popular route.
They also said services would be extended from Cardiff through to Penzance, better connecting south west England with south Wales.
This is part of wider December timetable change improvements being made by Great Western Rail across the south.
Mark Hopwood, Great Western Rail's managing director, told the BBC the new timetable would "provide our communities with the help and support they need, as together we rebuild and renew for the future".
He added: "Good rail services are key to economic recovery and to decarbonisation."
In future, the rail operator said it can provide extra, up to 12-carriage, capacity for events at the Principality Stadium.
Jess Morden, MP for Newport East, also told the BBC she thought the return of the half-hourly services between stations in south Wales and London was "really important".
"We're seeing more people now using the trains again and it's really important in terms of climate change and decarbonisation."
