Gomes has been followed out the Camp Nou door by goalkeeper Jasper Cillessen, who signed with Valencia on Wednesday in €35m transfer.
Barca also finalised the departure of Marc Cardona on Tuesday. The young forward has joined promoted La Liga side Osasuna for €2.5m after spending last season on loan at Eibar.
The sales edge the club over the €60m they needed to bring in before the end of the month to balance their accounts for the 2018-19 season.
Gomes, 25, spent last season on loan at Premier League side Everton having fallen out of favour at Barcelona, who he joined from Valencia in 2016 for €35 initially.
His performances in England drew interest from elsewhere -- notably West Ham United -- but the Portugal midfielder said it was always his desire to remain at Goodison Park.
"It wasn't hard to decide, it was an easy decision and I'm very happy to have made it," Gomes said.
"Last year was a really good experience for me. I just wanted to feel part of something special and I found it here. It was good for me at that moment and right now, after signing for Everton, it's even better."
Gomes made 78 appearances for Barca and won four trophies, but was never able to win a regular place in the side. Criticism from fans led him to reveal that life in his second season at the club had become "a kind of hell."
Meanwhile, the Cillessen deal will eventually see goalkeeper Neto move in the other direction. Barca will pay a fee in the region of €25m for the one-cap Brazil international.
However, the Catalan club must wait until July before finalising that part of the agreement due to their need to bring in money before the end of June to balance their accounts before starting afresh next month.
Barca signed Cillessen from Ajax in 2016 to provide competition for Marc-Andre ter Stegen following the sale of Claudio Bravo. The Dutch goalkeeper has done well when he's played -- mainly in the Copa del Rey -- but has failed to oust the German from between the posts.
Cillessen, 30, made 32 appearances for Barcelona in total and helped them win the Copa del Rey twice. He was also a runner-up in the same competition in May when the Blaugrana lost to his new club Valencia.
Before that final, he had already made it clear that he wanted to leave Barca this summer in search of regular first-team football ahead of next year's European Championships.
There was strong interest from Portuguese side Benfica but they were never willing to match the €30m Barcelona were asking for.