"I'm delighted now that everything is signed and I'm going to be spending the next few years at Everton," the 33 year old said.
"When you are on loan, it is never the same as being a signed player. I was really settled last year - but now I am an official Everton player and it feels really good."
Everton boss Martinez said: "We all know the type of footballer that Gareth is and the type of person that he is. He will fit perfectly well into what we are at Everton. It is a great way to start pre-season."
Barry added: "From the moment I signed last year, I settled in straight away.
"There is a fantastic history here and it was brilliant working with the manager."
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