The 21-year-old has only made five appearances for the Blues this season and is keen to use his time at Newcastle to show what he can do.
Speaking following his move, he said (as reported by Sky Sports): "When I was a child, I used to play with my friends in the streets and I always dreamt [of] being in a club like this one. And now the dream has come true.
"It's a really important time in my career and I hope I can do my best. I'm here to learn and show my potential is not just potential, but that I can do things in the future."
The young midfielder left home at the age of eight to pursue his dreams and joined Brazilian side Fluminense in 2009 before signing for Chelsea in 2015, making the move to London at the age of 19.
Newcastle's new signing is eager to make the most of his opportunity to get game time in the Premier League under manager Rafa Benitez, who has been interested in the young Brazilian since last summer.
"I will do my best because it's a big opportunity. I want to grab this opportunity and all that comes with it," he said, as quoted by the Evening Standard.