PSG's acquisition of the two players for huge sums - £200m for Neymar and £166m for Mbappe - is being investigated by UEFA and the stiffest punishment would be exclusion from the Champions League.
But Real have been long-time admirers of both Neymar and Mbappe, are keeping a close eye on the situation and are ready to take one of them if PSG need to make a quick sale, according to Spanish newspaper AS.
PSG have previously been investigated over FFP, but the latest set of leaks published by German magazine Der Speigel have thrown the French giants back into the spotlight.
While they would want to keep both their superstars if possible, missing out on the Champions League is unthinkable for the Ligue 1 champions.
Real are looking to strengthen their squad and bring in a big name following the sale of Cristiano Ronaldo to Juventus in the summer.