But it is Barca who have secured the 16-year-old, who will now be part of the Juvenil A side having signed a three-year contract.
Barry has spent 10 years at West Brom, and made his debut for the Championship club's Under-23 team last season.
And De Jong thinks he can transition seamlessly from the Eredivisie to La Liga.
“I was proud to join Ajax. I had a great time there and the tactical work is top level. The philosophy is very similar to at Barca, evidently because of Cruyff,” the 22-year-old told Barca's official website.
“It means a lot to me that a club as big as Barca has done all it has done to sign me. It makes me feel very proud.
“It was always the club where I wanted to play and now it’s happening. Barca have always tried to play attractive football and to win a lot of titles playing with the best players of all time. It has always been my dream to come here.”
De Jong's international manager Ronald Koeman played for Barca between 1989 and 1995, and De Jong has revealed he spoke to the former Everton boss before he completed his move.
“He was very enthusiastic when I told him I was going to sign for Barca. He told me I should concentrate on football because all eyes will be on me. People will want a lot from me.”
The midfielder could line up for the Catalan side when they take on Chelsea in a pre-season friendly on July 23.