The former Reds winger has backed his old manager to succeed in the Santiago Bernabeu hotseat.
The Spanish trainer has been appointed at the Estadio Santiago Bernabeu to replace Carlo Ancelotti, which has been treated as a surprise in some corners.
Benitez’s last role was at Napoli, with the ex-Reds boss not securing Champions League football for the San Paolo outfit in 2013-14 and then leaving the Serie A side.
However, Kewell has backed Benitez to get the best from the Madrid squad and stated that he will win silverware in the Spanish capital.
“He’s a great guy, a great manager, I love him,” Kewell told AS.
“He’s the perfect coach and he will be successful at Real Madrid. He is very strong mentally and he understands football very well indeed; he knows how to get the best out of his players.
“He was always very straight with us, always honest and sincere. If he doesn’t like something – or if he does like something, he will say so; he always tells the truth.”
Kewell and Benitez won the Champions League together with Liverpool in 2005, in the Merseyside club’s proudest day in recent memory.
The Spanish trainer has a real job on his hands to dethrone a dominant Barcelona, who won a momentous treble last season in Luis Enrique’s first campaign in charge.
Madrid have seen Iker Casillas leave this summer to join Porto, while continued speculation and controversy away from the action will be something that Benitez will have to overcome if he is to succeed at the Bernabeu.