The Manchester City midfielder completed a season-long loan move to Goodison Park before yesterday's 11pm deadline.
"The deal was done late but it was something that I always hoped would get over the line," Barry told the club's official website. "I'm really looking forward to meeting up with the lads and helping Everton to progress.
"I know all about Everton's history and it's a fantastic club. I've enjoyed playing games at Goodison Park, the atmosphere is always fantastic."
The 32-year-old has dropped down the pecking order at City following the arrival of new manager Manuel Pellegrini.