This year's tournament saw audiences increase to their highest level for 13 years, with an average audience of 4.7 million per match.
This continued the trend of year on year growth and in total over 30 million people within the British Isles watched some of this year's tournament.
"Viewing figures continue to grow year on year and we look forward to continuing to work in partnership with the Six Nations to build interest even further through the BBC's unparalleled offering of TV, radio, online and interactive services."
John Feehan, Chief Executive of the RBS 6 Nations, commented: "We are delighted that BBC Sport will maintain, extend and enhance its coverage of the RBS 6 Nations, the world's biggest annual rugby tournament, for a further four years to March 2017.
"The RBS 6 Nations is a major sporting event combining traditional rugby values with modern means of fans' support, this could not be possible without the support of BBC Sport, RBS and our other partners and broadcasters."