One large office has been incorporated into the home changing room and a part of the club shop has been added to the visitors' changing room.
The existing referee changing room has been refurbished and additional space and a shower have been added to enable female officials to be catered for.
The medical facility has also been renewed with a larger and more modern space.
This work will allow the temporary changing facility to be removed so that there is a better and permanent provision.
Mr Phil Llewellyn, Chairman of the club, was delighted to work with the WRU and the Balconiers to improve facilities and to ensure the new installation was made.
He said: "Last year there were 70 events staged at St Helens outside the normal use of rugby and cricket. This intensity of use is largely by community and school organisations and events.
"It is a tribute to the pitch at St Helen's, which is acknowledged to be the best grass pitch in the UK."
Last year's events included Wales against England and Wales againstt France age group games.
The WRU grant was conditional upon the new facility being used by the community game as it has been over the last five years and for player development by schools, colleges and competition finals.
The work is being completed on schedule and will be ready for August.
Mr John Williams, Chairman of The St Helen's Balconiers, said: "We were delighted to support Swansea RFC in the redevelopment of the changing rooms and to bring them up to the standard expected by the modern day player.
"This has now been addressed and to the benefit of sport in Swansea"