Carney (28yo) is currently serving a controversial eight-match ban after internal Salford investigation, for racist abuse towards Toronto prop Ryan Bailey during a Challenge Cup game.
He has already served three matches of the ban, and would be available to play for Rovers well in advance of their Qualifiers campaign, where they hope to regain their Super League status.
A Red Devils statement read:
"Salford Red Devils can confirm that winger Justin Carney is to join Hull Kingston Rovers with immediate effect, after the club reached an agreement with the player's representatives.
"The player leaves by mutual consent following the conclusion of an internal investigation.
"Carney was suspended for eight games by the Rugby Football League after admitting using racial language, leading to his sending off in the Ladbrokes Challenge Cup against Toronto Wolfpack last month.
"The club will be making no further comment."
Justin was a fan favourite and will be deeply missed.