It was hardly the best kept secret in football as he was pictured in the stands at Goodison Park to see his new side lose 1-0 to Chelsea on the opening day of the season.
Now the Toffees have announced the signing of the Belgium international.
And of course, they had to post the obligatory video that featured the Rihanna song 'What's My Name?'
The 20-year-old midfielder has agreed a five-year contract at Goodison Park and becomes the Toffees' fifth summer signing after James Tarkowski, Ruben Vinagre, Conor Coady and Dwight McNeil.
Speaking to evertontv, Onana said: "It feels great to join Everton. I know it's a big, big club, one of the biggest in England.
"It's something I want to be part of for many years."
Onana highlighted manager Frank Lampard as a key reason behind the move, saying: "He played at the highest level, won many things and was a midfielder, too.
"It means a lot to have interest from him and I think he can teach me many things."
The midfielder had plenty of options at his disposal this summer with West Ham having a £35million bid accepted by Lille.
The Hammers thought they had won the race to sign him, before Everton came in and matched that offer.