The RNLI wants to replace Burry Port's aging boathouse and bring both its lifeboats under one roof.
The centre will be built between the existing lifeboat station and the western slipway.
Roger Bowen, Burry Port Lifeboat operations manager, said it was "the start of an exciting new chapter in the station's 71-year history".
He added: "The RNLI will now proceed with the detail design and construction phase of this iconic building."
The centre will include modern training and changing facilities for the volunteer crew, which will help speed up launches, a workshop and a public viewing area.
Plans for a new lifesaving centre in Carmarthenshire have been approved by the council.