The 31-year-old, whose contract expires at the end of 2017, has been told by Castleford boss Daryl Powell that he is not part of his team's plans for 2018.
The New Zealand-born player was not included for Saturday's Challenge Cup 53-10 victory over St Helens.
The former England playmaker was dropped for three games in March after an "internal investigation".
"I have nothing but love for Cas as a club, the players, coaches and back room staff, including the fans. It's a place that will always be close to my heart," said Chase.
"I have Cas to thank for making me fall back in love with my childhood dream again."
Chase returned to Castleford last July after leaving Championship side Leigh Centurions, who he joined from Salford after having his contract terminated following a "disciplinary procedure".
Chase, capped eight times by England, won the 2011 Man of Steel during his initial four-year stint with Super League side Tigers.
His loan agreement with Widnes does not have a call-back option, and Chase will not be able to play against Castleford this season.
Widnes Vikings have signed Castleford Tigers half-back Rangi Chase on loan until the end of the season.