The Verdiblancos have paid Fluminense €9.5m in total for 100% of Bernal's rights, made up of an €8.5m transfer fee plus €1m in Spanish tax obligations. The Brazilian club retains a 5% sell-on clause on any future sale. Bernal, who also holds an Italian passport, arrives to fill the void left by Sergi Altimira's departure to Sporting CP.
Bernal landed in the Andalusian capital on Monday afternoon before heading straight to the Ciudad Deportiva Luis del Sol, where he put pen to paper on a five-year contract that ties him to the Verdiblancos until 2031. He then fronted up for his first interview as a Betis player on the club's official channels.
The midfielder made no secret of his delight at finally getting the move over the line.
"Thank you so much for the welcome. I'm really happy, I waited a long time for this and now we're here," he said.
Bernal also revealed Betis had been tracking him for some time before finally striking a deal.
"Of course. That's why I came here with a lot of excitement, to join a club that's going to fight for important things, and here we are, for the best," he added.
With Betis preparing for a first Champions League campaign, Bernal is well aware of the scale of the challenge ahead.
"It's something really special for everyone, fighting for something historic which is very important for Betis, competing at the top, and we're looking forward to it," he said.
Asked about taking the leap into European football, the midfielder credited timing and ambition in equal measure.
"The moment arrived and I had to take it, joining a big institution like Betis, and whatever God wills," he said.
He closed out his unveiling with a message for the Betis faithful ahead of the new season: "I'm really happy, I've genuinely waited a long time for this. We're here now and I can't wait to be out on the pitch with the stadium packed with fans."
Bernal becomes Manuel Pellegrini's first confirmed arrival of the window as Betis look to strengthen a squad that will compete on multiple fronts next season, with further additions expected before the transfer market closes.