Teixeira has come through the ranks at Benfica, playing for their ‘B’ team before making his first team debut in the Champions League fixture against Bayern Leverkusen in December, 2014.
Now signed up to a long term contract, he spent a spell on loan with Vitora de Guimaraes last season.
He has represented Portugal through the junior ranks up to and including Under-21 level, making 30 appearances in total across the various age groups.
Discussing the 22-year-old, Head of Football Development and Recruitment, Kevin Thelwell said: "He's a really exciting player. He's a strong, highly technical young player.
"He's played a lot at Benfica B and he's also had loan experience with a professional team in Portugal's first division.
"If you're talking about youth development, and who are the very best, then Benfica will be right up there.
"They have a fantastic track record of developing young players and players succeeding, not only with them, but all over the world.
"We think Joao can play in a number of positions and we think he can really improve our group.
"I think it's a bit of a coup for us to get him and I think he will integrate into the group really quickly once he picks up a bit more of the language.
"He's a very bright boy, he's enthusiastic and I'm really looking forward to seeing him perform."
Football at Championship level comes with a tough reputation but Thelwell believes that Portuguese star will be able to adapt.
"I think there will be a case of some adaptation because the Championship is so different to every other league, there's a lot of pace and there's a lot of power," he explained.
"The one thing you can guarantee is, if you've got good players and they've got a high technical ability, then they should be able to cope in the league.
"I'm sure we'll have to be careful with him in the first instance and we may have to protect him in certain games but I think he's got all of the tools to be a success at this level."
