The 35-year-old had his contract with the Turkish club terminated last week after he fell out with coach Aykut Kocaman over his complaints on Twitter.
"For eight years I tried my hardest for the team," he said. "I don't know what the future holds but I can say this from the bottom of my heart: I will always be a Fenerbahce fan.
"I have no bad feelings towards anyone and hope Fenerbahce win the league and Europa League trophies.
"I have no problem with the chairman [Aziz Yildirim]. He loves the club and his decision is always made with the club in mind."
De Souza won the Turkish Super Lig title three times with Fenerbahce.