Assistant coaches Mick Cassidy and Dave Banks and strength and conditioning boss Clive Brewer have also agreed new two-year contract extensions.
Betts, the former Wigan and Great Britain forward, joined the Vikings in November 2010 after a five-year stint in rugby union with Gloucester and, although Widnes finished bottom of the table at the end of their first season back in Super League, new chief executive James Rule believes a platform has been laid for future success.
"I have been immensely impressed with the performance environment that has been created by Denis and his coaching team and I am delighted that we have secured their services until the end of the 2014 season," Rule said.
"When you consider that just 12 months ago the club had to undertake the transition from semi-professional rugby into a full-time professional Super League organisation, the progress that has been made is nothing short of remarkable."
Betts added: "From day one, my vision has always been about putting something in place and building the foundations to make this club stronger.
"The reality is these things take time so I'm really pleased that our chairman Steve O'Connor and chief executive James Rule believe I am the right person to continue this work and take things forward.
"If you have ambitions of achieving anything, what you need is consistency.
"We have taken some big strides and there is a lot of work still to do but we are moving in the right direction and this can only be good for the players, the coaching staff and the club."
- Sports & Recreation
- Mick Cassidy
- Super League