The 23-year-old defender has joint citizenship with Italy, but now appears set to fully commit to the Selecao.
“Today is one of the best days in my career," wrote Ibanez on his social media profile.
“I've dreamed of wearing the Brazil shirt since I was a kid and now on September 9 that becomes a reality.
“These are the fruits of my labour, but also those of several other people, so it is an achievement for us all! I have immense happiness."
Brazil face friendly matches against Ghana and Tunisia, to be played in France on September 23 and 27.