Kenedy also spent the second half of last term on loan at St James' Park and he will now return to the club for a full campaign.
"I am so happy with this interest from Rafa Benitez, that he came back for me. I want to keep it going, the work that I did here before, for the new season," Kenedy told the club's official website.
"I have received many, many messages on social media from the fans. They made me feel appreciated, so I wanted to come here in this new season and give everything on the pitch."
Manager Benitez added: "I'm really pleased to have Kenedy back with us. I'm sure every fan will be happy with this signing. Hopefully he can keep playing at the same level that he reached with us last season. I wish him all the best for his time here."
Kenedy featured 13 times for Newcastle last season, scoring twice and winning the club's Player of the Season award for March.