Department for Transport Ireland said the MetroLink project would “transform public transport in Dublin and improve connectivity to national rail links”.
It is expected to become operational in the early 2030s.
Transport Secretary Eamon Ryan said he was confident the project could be delivered on time and on budget.
He added that the €9.5bn (£8.16bn) cost estimates were “overly cautious and conservative”.
Mr Ryan described the MetroLink plan as a “mega project”, which he claimed would transform public transport in Dublin.
The project aims to connect the north and south sides of the city.
It will be 19.4 kilometers long with 16 stations mostly underground, running from north of Swords to Charlemont Street in the south of Dublin city centre.
The department said trains would run every three minutes during peak hours, capable of carrying up to 20,000 passengers per hour in each direction.
It will interchange with the DART (Dublin rail service) and Luas (tram service) transport systems.
By 2050, the Irish government estimates it will provide more than one billion carbon-neutral, fully electrified passenger journeys.
A design proposal will be submitted in September, with the Department of Transport recommending its approval.
