The 22-year-old midfielder impressed as Ajax won the Eredivisie title and reached the Champions League semi-finals last season.
Barcelona announced the signing of De Jong in January for a 75-million-euro ($84.3 million) fee on a five-year deal which started on July 1.
"Of course I was thinking about other clubs which were interested, but it's a normal process," he said.
"I considered my options, which was best for me, Barcelona came to see me, they convinced me...
"The decision was easy for me. They said they had every confidence in me, that they thought I would be a key player for Barca in the future."
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Reigning Spanish champions Barcelona have been looking to strengthen after a humiliating Champions League semi-final loss to Liverpool, and president Josep Maria Bartomeu also said on Friday they had held talks with Atletico Madrid over a possible signing of French forward Antoine Griezmann.
De Jong thinks that playing with the best players in the world, like five-time Ballon d'Or winner Lionel Messi, will help him improve.
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"Of course, he (Messi) is the best," he said. "I'm very happy to play with him and I'm also looking forward to playing with the whole team.
"All the players here are really talented, not just Messi."
He joins a long list of Dutch players to sign for Barcelona, initiated by Johan Cruyff's moves there, also from Ajax, as a player in 1973, and as a coach in 1988.
"The Netherlands and Barcelona have always had a connection," De Jong added.
"It's about playing in a similar way with the philosophy of Ajax and of Barca, which for me is obviously great."
De Jong was a mainstay of the Ajax side last term, scoring three goals in 52 appearances, while also breaking into Ronald Koeman's Netherlands team and winning nine international caps.
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