Stephan Andersen will join Brondby in January after Charlton agreed to allow him to return to his homeland.
The Denmark international has found opportunities at The Valley scarce since joining Charlton in 2004 from AB Copenhagen.
A proposed deadline day loan move to Leeds recently fell through but he has now secured a permanent exit from the Premiership as he looks for first team football.
Charlton boss Les Reed admits he is disappointed to see Andersen leave for pastures new but accepts his desire for regular playing time is a noble one.
"I am sad to see Steph go but glad that he will be given an opportunity to play regular first-team football at a high level," said Reed.
"It has been frustrating for Stephan as Scott Carson has been in outstanding form this season and there have therefore been limited opportunities for him to play in the first team.
"It's better for him and his own career development to take an opportunity like this and it also allows the club to move on with Scott and Thomas Myhre as our first-choice keepers."