The versatile forward enjoyed 10 seasons at his home region playing in 167 first team matches, taking him to eighth in the all-time appearance list.
During that time Cook crossed for 17 tries and played an instrumental role in winning the 2018 European Challenge Cup against Gloucester in Bilbao.
However, he will make the move to Jersey this summer and is looking forward to a new chapter in his career and the life experiences that come with it.
Cook said: “It’s sad to be leaving Cardiff Blues, particularly given the current circumstances and not being able to have a send off with my teammates, all the great people at the Arms Park, and of course the supporters.
“However, I look back on my career at the Blues with immense pride. This is my home region and it was always my dream to play professional rugby.
“To do that for 10 years at Cardiff Blues was amazing and I will always be grateful for the opportunities given and the friends I made along the way.
“There are so many stand out memories from my first senior appearance, against Exeter Chiefs, to my 150th with a great win against Munster and my family in the crowd, and of course our journey to winning the European Challenge Cup.
“Cardiff Blues will always remain a massive part of me but I am now looking forward to a change of environment and relishing the challenges ahead.”
Cook’s versatility has been a major benefit over the years, however opportunities were limited during the last season.
He last featured against Calvisano in the European Challenge Cup at the Arms Park in January.
Cardiff Blues head coach John Mulvihill has paid tribute to Cook’s contribution to the region and has thanked him for all his efforts.
He added: “Macca has been a great servant of the club for the past 10 years. He has always been a very good team man and has contributed to the success of Cardiff Blues both on and off the field of play.
“The past two seasons have been tougher for him in terms of injury and this has limited his time in the jersey.
“Despite this he has continued to selflessly assist his teammates and coaches in their preparation for games.
“Now back to full fitness and with the desire of a new challenge we wish him all the best for his future and hope that in the near future we can celebrate and congratulate him on his career at the Cardiff Blues.”
