Cardiff Central station is to undergo a multi-million pound upgrade to ease crowding and congestion.
The Department of Transport announced £58 million to improve access and upgrade platforms to cope with longer trains.
The UK Government says the upgrades will "ease crowding and congestion through the station during peak periods, drive forward regeneration and enable longer trains with more seats to serve the capital."
The announcement comes two years after Mr Grayling was criticised for a controversial decision to scrap plans for electrification of railway lines in areas of the UK including Wales.
The news was welcomed by Welsh Secretary, Alun Cairns MP, and he repeated the UK Government's pledge to progress plans for a West Wales Parkway station.
The UK Government said this investment intends to build on the £5 billion the UK Government is investing on improving journeys for passengers on the Great Western Mainline between South Wales and London, targeted at introducing more reliable and faster services, new trains and more seats.
The UK Government says it wants to build a new West Wales Parkway station, near Swansea, to boost connectivity and capacity for passengers across the south and west of Wales.