Sources at Goodison Park confirm that the club have made an enquiry about the 26-year-old Nigerian striker but insist no formal bid was made for the player, who is valued at more than £11million.
But Middlesbrough have made it clear that the player is not for sale and Everton are now very unlikely to continue their interest.
Yakubu is believed to have had showdown talks with Boro' boss Gareth Southgate today, and expressed his uncertainty about his future at the Riverside.
But with the Premier League season just two days away, Boro made it very clear to their much-wanted hitman, that he is not for sale.
Several clubs have tracked Yakubu this summer, including Manchester City, West Ham and Portsmouth.
Now Everton have become involved, but the answer to all enquires has been the same - no deal.