The new movie is the third and final instalment in the series, which has raked in hundreds of millions of dollars since starting in 2015.
Dornan plays Christian Grey and acknowledged the significance of the movies -but admitted his optimism about future work.
“It’s tough in some respects, but it’s also really nice and kind of bittersweet, I guess,” he told ET.
“I think when you finish any movie or TV series or whatever, you’ve invested so much [time] into the character and the job itself and the other actors and the crew.”
He added: “That’s sort of tenfold if it’s a sequel or trilogy of films. For the most part, we had the same crew back [and] obviously the same actors back, so you’re that much more invested in these people and their lives and that much more closer to them. So, it makes it harder to say goodbye.
“Because you’ve been playing this character for a few years, whatever it’s been, four and a half years, you’re quite happy to say goodbye. Because it’s nice to put that aside and move on.”
Dornan had previously ruled out rumours of more Fifty Shades movies in the future.
In an interview with ITV’s Lorraine, he said: “[EL James] wrote the first two books again from Christian’s perspective, but I guess we’ve already seen… we’ve done those films, the same story, so they won’t do that again.
“Unless Erica keeps writing… but Dakota and I are… particularly me, I’m getting too old for this.”
The new film has been lambasted by critics, with some picking up on a perceived lack of enthusiasm from Dornan.
Fifty Shades Freed is out now.