The French-born Benin international has clocked just 50 minutes of Premier League football over three games for Cardiff this season after appearing in half of the club's games in the Championship last term.
He now drops back to the second tier to join Rovers, who will look to make the move permanent in the January transfer window.
"When I was younger, I used to pick Blackburn when I played videogames," Gestede told Rovers' website.
"Of course we played against them last season, so I know it's a good club, with a good atmosphere. The fans are amazing, like they are at Cardiff, and maybe that's why I chose this club."
Gestede, 25, could make his Rovers debut against Leeds United this weekend.