A £1.5 million rising to £2 million offer has been accepted by Burnley, but for Gray to be able to play in today's match against Watford, an emergency loan deal between the two clubs has been agreed. Gray will then sign permanently next week.
The 30 year-old who played for Sheffield United and Sunderland said, "I'm delighted to be at Charlton, and I just want to get started,"
"It's great news that everything has gone through in time for Saturday's game, and we'll have to see whether I'm in the squad."
"I'm at the stage of my career where the chance to go to a club that had been in the Premier League for a long time, and has a great chance of getting back there, couldn't be ignored," he said.
"Everyone wants to play in the Premier League, it's where I want to play, and hopefully I can help the club get there."