The 24-year-old Morocco international left-back has put pen to paper on a five-year deal at St. James’ Park.
Lazaar came through the youth set-up at Italian club Varese and spent two years in the first team before joining Palermo in January 2014, initially on loan.
He helped the Rosanero win Serie B at the end of his first season and has been a regular in the top flight, making a total of 76 appearances and scoring three goals during his time at the Stadio Renzo Barbera.
“I am very happy to be at Newcastle United,” said Lazaar.
“I’m proud to sign here because Newcastle is a great team in England.”
If you missed it earlier, United have confirmed that their EFL Cop third round tie with Wolves will be played on Tuesday 20 September, kick-off at St. James’ Park is 7.45pm