The 21-year-old made the move in search of more game-time according to Roman Lingnier, who has a working relationship with Mothiba's agent.
"Mothiba has gone on loan to Ligue 2 side Valenciennes until the end of the season," Lingnier tells snl24.com/kickoff from France.
"He's happy and he moved there to play more football, and he'll come back at the end of the season. What is positive is that Lille have new investors and since January they've become a big attraction team."
Mothiba was promoted to Lille's first team at the beginning of the campaign after impressing in their development ranks, having initially joined the side from the now-defunct Diambars academy, which was based in Boksburg, Johannesburg.