Juno arrives for third Boro spell
The Brazilian star has joined Boro on a four-year contract in a deal costing é¼6 million (£3.7 million) and follows the arrivals of George Boateng and Geremi, who met the media on Monday.
Juninho admitted that he was delighted to be back on Teesside.
"I am very happy, I was on loan second time, which was not the same," he said.
"I love the people, I had excellent treatment from the fans last time.
"I am still the same player - a lot of people said that when I broke my leg I could not be the same, but that is rubbish.
"I hope to give a lot back to the fans, I decided to sign for Middlesbrough again because it feels like home and the ambitions are still here.
"It is time for Middlesbrough to win something, they are bigger than before.
"I think it had to be Middlesbrough, I am not sure I would have gone anywhere else in England.
"I spoke to Steve [McClaren] after the Brazil v England game in the World Cup and he told me about the ambition of the club and he said I could go back to Middlesbrough and I was very happy with that."
McClaren was also very happy to welcome his latest acquisition.
"I am absolutely delighted," he said. "We have been searching for some time for a special player who can win football matches.
"We are delighted to have brought him back, we believe that the timing is right for him to come back
"We are building a good team here and believe he is the final piece of the jigsaw.
"I know the adoration he has here and we have been keeping an eye on his situation for sometime and I also kept an eye on him during the World Cup.
"It shows the ambition that the club has by signing him, they have realised how ambitious I am and I believe we have improved the squad dramatically.
"We are here to win football matches and I believe we have brought players in to do that, we do want to just improve the quality of our football.
"Winning football matches will lead to winning things and that is what we want."