The 20-year-old has seen his chances limited at the KC Stadium since Steve Bruce arrived in the summer.
He spent time with Burnley earlier in the season, but he now he has been snapped up by Blackburn as they look to mount a late charge towards the play-offs.
Stewart's agent Peter Morrison of the James Grant Group, confirmed that the deal had been concluded.
"He has signed a deal until the end of the season," Morrison told Sky Sports.
"This is a fantastic move and opportunity for him, to sign for a massive club such as Blackburn.
"They have huge ambition and highly respected top young manager and the chance for Cameron to be a part of that was too good an opportunity for him to turn down."