The 17-year-old Belgian has emerged as a player attracting attention in England after progressing into Genk's senior setup and continuing to develop with Jong Genk.
Manchester United and Newcastle United had already been linked with De Wannemacker, while Nottingham Forest have now joined the Premier League clubs tracking his progress.
On the Minute reports that Forest have added the midfielder to their watchlist, with no formal approach made for the teenager at this stage.
De Wannemacker can operate as an attacking midfielder or as a No.8 and has gained experience with Genk's first team alongside his regular involvement at youth level. He made four appearances for Genk's senior side last season as his progress accelerated.
The Belgian youth international has also captained his country's Under-19 side, adding to his growing reputation as one of Genk's promising young players.
Genk are in a strong position to decide his future, with the club keen to continue developing him rather than rushing him into a major move.
The interest from three Premier League clubs nevertheless underlines how quickly his profile has grown.
Manchester United are understood to be among the clubs impressed by his potential, while Newcastle's recruitment strategy has increasingly focused on identifying young players who can be developed over time.
Forest's involvement gives De Wannemacker another suitor to consider if the clubs eventually decide to make their interest more concrete.
For now, the situation remains at the monitoring stage rather than an active transfer battle. There has been no formal offer, leaving Genk with considerable control over the next step in the teenager's development. The club can therefore assess the interest without having to respond to an immediate bid, while continuing to develop the player internally.
With three Premier League clubs now keeping tabs on him, however, De Wannemacker's performances are likely to attract increasing attention as the season progresses.