The proposed improvements will modernise the station and support long-term passenger growth, while still complementing the history and heritage of the building.
Plans include a larger concourse to increase capacity, improve passenger flow and access through additional gate-lines, and help customers link up with other ways to travel.
Planning and a decision on the full business case are expected in autumn this year.
Enabling works, which are needed at the southern side of the station to pave the way for full construction works, are expected to begin later in 2025.
Alexia Course, Chief Commercial Officer at TfW, said: “The proposals for the station form part of a wider significant investment going into transforming transport in central Cardiff, including ambitious regeneration plans.
“We’ve submitted the full business case for the scheme and we’ll soon be submitting the planning documents, and if this is approved, we can progress with the delivery of the enhancements.”