Hamer will join the Championship winners on a four-year deal once his contract at The Valley expires at the end of June, and the former Reading trainee has admitted that he will be fulfilling a dream by moving to a top-flight outfit.
The 26-year-old told the club's official website: "Being involved in Premier League football has always been a dream of mine.
"It's fantastic to be here. It was an opportunity that was too good to turn down for me and I'm looking forward to coming on board and improving myself as a player."
Hamer leaves the Addicks having made 121 appearances for the club.