Speaking on the extension Willis said: "I am delighted to have signed a contract extension with the Dragons. When I came here two years ago I felt that this was a young team who wanted to develop and improve, I felt that I could help contribute towards this growth.
"Over the past two seasons I feel we have made considerable progress and this has been reflected in our performances this season. The team here has a great spirit and all are looking to improve both individually and as a unit and I am pleased that I am going to continue to be part of this development going forward."
Thomas, capped 22 times by Wales, who joined at the start of the 2009/2010 season from the Scarlets, and has played 21 times for the Dragons added: "I am really pleased to have signed a contract extension with the Dragons. I have really enjoyed playing for the team this year and it's been great to have got a run of games under my belt.
"The team and organisation are looking to improve all the time and the new training facilities are just one example of this. There's a great team sprit here and I am delighted that I am going to be a part of it over the next two seasons."
Speaking of the signings Rugby Manager, Robert Beale said: "It's great news that both these players have agreed contract extensions with us. Tom has been an excellent Captain for us both on and off the field, whilst Gavin has also been a major performer for us this season.
"They are key players in terms of performances on the pitch and the experience they bring to the organisation and in helping develop our younger players. We are looking to continue with this development and growth and I am confident both players will be key contributors to this over the next two years."