The Belgium international signed for the Red Devils for £27.5m after submitting a transfer request at Goodison Park on deadline day.
While Martinez has claimed that the club wanted to keep Fellaini, the Spaniard has insists that the player leaves the Merseyside outfit with the club's "blessing".
"You always want to keep your best performers and Marouane has had five outstanding seasons at Everton, but he leaves with our blessing," Martinez said in a press conference.
"I think everything was done on our terms and I think that's what matters, and what's important. We wish him well, but I do feel that when you lose a player, you need to end up with a better shape in the squad, and I think that's what we achieved."