The 22-year-old joins the Magpies from German Bundesliga club TSG 1899 Hoffenheim.
Joelinton netted 11 goals from 33 appearances in all competitions last season.
“I’m really happy to be here,” Joelinton said.
“I know (wearing the number nine) is a huge responsibility, the great Alan Shearer, the team’s biggest idol wore it. I know it is a big responsibility, but I am prepared.
“I know it is a large investment that the club has made in me, and that comes with a huge responsibility.
“I know that everybody at the club has faith in me having brought me here. I hope to contribute on the pitch. I am happy and prepared.
“Rest assured there will be no shortage of desire and dedication to score lots of goals and honour the number nine shirt.”
Joelinton is new boss Steve Bruce’s first signing having replaced Rafa Benitez this off-season.
The Brazilian’s signing smashes the previous club record fee of £20m paid for Paraguay playmaker Miguel Almiron.
“The kid has got an exciting time ahead of him,” Bruce said.
“He is a smashing young player and we are obviously delighted to get him.
“It is been going on for a little bit now, so to get him is great for everybody.
“He has got everything that a modern-day player wants.
“He is big, strong and athletic, and of course he’s got age on his side too which is vitally important.”