The former Wigan Warriors and Great Britain International has handed a two year deal at The Stobart Stadium.
Chairman Steve O’Connor said: “The board and I are aware that the appointment of our coach for Super League is one that is crucial to our development as a club and its future success.
“The team considered this decision very carefully, we looked at a number of other candidates, it was abundantly clear during this process that Denis was the best fit for our club.
“He has the right values, ambition and capabilities to take this club forward and we are absolutely 100% behind him.”
Betts took over at the Stobart Stadium in the close season and has won half of his eight league games in charge.
Widnes Director of Rugby Paul Cullen said: “Denis Betts will take full responsibility for the identification and selection of players for our entry into Super League. I will be supporting him with the recruitment of these players.
“On a personal note, I am confident that Denis will grow to be one of the best Super League coaches in the UK.”