Moffett, who is one of the two WRU delegates on the Six Nations Committee, played a central role in helping to clinch the four year extension to the current deal, which still has two years to run.
"This is fantastic news for the Six Nations Championship and for Welsh rugby. This deal provides financial certainty for all countries for the next six years," said Moffett.
"The BBC's long association with, and expert coverage of, the Championship has played a vital part in developing our tournament into one of the world's top annual sporting events.
"Playing in the Rugby World Cup finals and the Six Nations Championship are the ultimate goals of all rugby players in Wales and this new deal will enable the WRU to plan for an even better future both on and off the field."
The deal extends the BBC's current contract as exclusive broadcaster until 2010 and comes hot on the heels of a 30% rise in average
audiences last year and further increases in the opening two rounds of this season's championship. Average UK audiences per match have reached 4.1m, up from 2.8m two years ago when the competition was divided between three broadcasters. Last Saturday's Calcutta Cup match between Scotland and England was watched by more than 8m viewers, one of the biggest audiences in the Championship in recent times.
"I view this as a further enhancement of rugby's good relationship with the BBC and here in Wales we will be seeking to further strengthen our links with BBC Wales as a result. We still have a further two years to run on our current Celtic League contract with them and they are also our partners for our autumn international matches," added Moffett.
"This deal shows that things are really on the up in rugby in this part of the world and proves we are getting to grips with matters both on and off the field."