The 26-year-old joined the club in 2020 in a £15m move from Norwich but has failed to establish his place in the side ever since.
Watford welcomed him on loan for the whole of last season as he made 36 appearances for the Championship side which is more than every other season combined whilst at Newcastle.
Northern Ireland manager Michael O'Neill spoke about the deal and how expects the full back to be in Brazil soon.
"Jamal is planning to join us later in the week after he completes his visa requirements and medical checks in Brazil," said O'Neill, confirming Lewis would report late for NI's upcoming Nations League fixtures against Luxembourg and Bulgaria.
"We wish him the best of luck in his new move to Sao Paulo."
Newcastle boss Eddie Howe also spoke on the possible move which would benefit both parties.
"Maybe the players that have been linked with a move, like Jamal Lewis could possibly leave, but certainly we hope no one else does.”