Boa-Morte was said to be on wages of at least £40,000 per week and had been at the club since January 2007 making 109 appearances for the Hammers, scoring only twice.
Speaking to the official site, Boa admitted it was a sad time for him to be leaving.
“I am sad to leave West Ham as I have made a lot of friends here. It is also a sad day for me to leave playing football in England after 14 years.
“I am looking forward to a new challenge. It is never too late to try somewhere and something different. There are high and low memories - the low ones only make you stronger - now it is a fresh start for me.”
For West Ham, of course I would like to see that they get back into the Premier League again.
“Last season, we fought to the end, but it was not to be. I wish all the best to my team-mates and for the club to get promoted.
“I would like to think people would have seen me always give everything for the team. I always tried to put my heart and head in for the team.”