Jamal joined Newcastle United from Norwich City in 2020 and has made 36 competitive appearances for the Magpies but has struggled to make his mark on the first team in recent years.
His last outing for the club was in August and he was unlikely to earn many minutes this season which left the door open for clubs to make a loan bid.
Lewis enjoyed the duration of last season on loan at Watford, playing 38 times for the Hornets in all competitions, bagging two assists.
He spoke about the move and how he cannot wait to get started at such an exciting club.
"I want to try and win Cups and push up the League. I'm super excited to meet all the Sao Paulo fans. I've seen some games and I can't wait to step out on that pitch," he said.
"The Premier League is intense, it's tough, it has a lot of quality, so hopefully I can bring a lot of that and contribute to Sao Paulo."
Lewis was originally expected to link up with Northern Ireland today ahead of their Nations League double-header with Luxembourg and Bulgaria but manager Michael O'Neill revealed that the Brazil move was on the cards.
"Jamal is planning to join us later in the week after he completes his Visa requirements and medical checks in Brazil. We wish him the best of luck in his new move to Sao Paulo."
