The 32-year-old actor portrays Sir Lancelot in the comedy film and got to fight a mythical, multi-headed snake monster and a triceratops as one of King Arthur's Knights of the Round Table.
Stevens admits it was tough work carrying out his stunts in his metal armour.
He told BANG Showbiz: "The biggest challenge was probably the armour, getting used to the weight of it specifically. It took quite a long time to get on. I rehearsed all the sword fights without the armour and got the hang of that but then doing it with the armour was very different, quite tiring. Even when you get out of it, you still feel very tired."
Dan also admitted it was tricky filming the fight scenes because the snake monster was created with CGI so when he had to shoot sequences he was swiping his sword at nothing and had to rely on director Shawn Levy's instructions.
The British star - who appears in the movie with Ben Stiller, Owen Wilson and Rebel Wilson - explained: "You just have Shawn yelling at you, 'It's coming from the left. It's coming from the right, duck!' Sometimes there's a guy with a tennis ball to give you direction, but other than that nothing."
