The England international signed for the French club in 2012 from Bradford, and has made 43 appearances for the Dragons, scoring 24 tries.
“I would like to thank the club and the fans for everything they have done for me and I’m still fully committed to the Dragons this season.
“Whilst I will be sad to leave, I am also looking forward to the future.”
Catalans headcoach Laurent Frayssinous expressed his sadness that Whitehead was leaving.
“I’m really disappointed to lose a such quality player,” he said.
“Since he arrived at the club, he has always given his best on and off the field to help the team.
“I’m sure he will stay in the heart of the Catalans fans but before his move, he has a job to finish under the Dragons jersey.”