The 32-year-old, who played a crucial role in the Toffees' Premier League survival in the 2022/23 season, is now free to listen to offers from other clubs.
Doucoure is one of 13 Everton players whose contracts expire this summer, as the club navigates financial constraints and a potential squad rebuild.
Despite his contributions, including his famous winning goal against Bournemouth on the final day of the 2022/23 campaign, Everton have opted not to activate his automatic extension clause.
However, a return to Everton remains possible. The club could look to renegotiate terms to keep the Mali international at Goodison Park, and new manager David Moyes may have a role for him in his plans.
"It's a difficult situation, to be honest. I never lie when I talk about my future. Obviously I've had a great time here. I don't know what's going to come next. I'm a free agent now so I have some possibilities," said Doucoure, as quoted by The Times.
"I will always cherish my time here and I will be very happy for what I did for Everton. Even if I leave, inside my heart I will always be a Blue.
"For the moment nothing has been discussed so let's see what's going to happen in the next couple of months. But it may be my last season here, so I want to enjoy it as much as I can and do the best I can."
With Doucoure's future uncertain, interest from other clubs is expected. As a free agent, he has the freedom to negotiate with potential suitors ahead of the summer window.