Brazil midfielder Allan reunited with Carlo Ancelotti on Saturday after moving from Napoli to Everton.
The transfer fee was not disclosed by the two clubs but media reports estimated it at 21 million pounds.
The 29-year-old Allan played 61 games under Ancelotti when the Everton coach was in charge at Napoli.
“It is a real pleasure to sign for Everton,” he said after agreeing a three-year contract at Goodison Park.
“It is a club with a rich history in the Premier League, has real ambition and then there is professor Ancelotti.
“He has done everything possible to bring me here. It is the size of the club and the name of the coach which means you don’t think twice about coming to Everton.”