The news comes only a week after Alexandrou's on-screen wife Natalie Cassidy, who plays Sonia, announced she was to take a break.
Of his departure, he told The Sun: "I've decided to leave the show to experience other aspects of my industry.
"Having turned 21, I feel it is an appropriate time to go. I owe everything to the show. I would love to come back one day - that is, if EastEnders will have me."
A BBC spokesman told DS: "James has been a fantastic member of the cast and he goes with our best wishes. His character will not be killed off and the door will be left open for a potential return."
Alexandrou's final scenes are scheduled to be filmed in the summer of next year and look set to be aired in the autumn.
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