He is portrayed by Peter Mullan.
Role in The Half-Blood Prince
In the sixth book Yaxley is one of the Death Eaters invading Hogwarts. He is present when Dumbledore is killed, and fights in the battle before leaving the castle with his fellow Death-Eaters.
Role in Deathly Hallows: Part 1
Yaxley served as one of Voldemort's spies inside the ministry. He placed Pius Thicknesse under the Imperius Curse on Voldemort's orders, so that Thicknesse could kill the previous minister and become minister for magic himself.
He appeared during the Death-Eater meeting in the beginning of the movie where he was telling Voldemort the date when Harry Potter was going to leave the house of his aunt and uncle.
But he was interrupted by Snape who told him that that was a false statement and the aurors tricked him by giving him a false date.
Later, he appears on the side of Dolores Umbridge at the Ministry of Magic where he is helping interrogating Muggle-borns. He is knocked out by Reginald Cattermole (who is actually Ronald Weasley in disguise) and discovers that one of the employees of the Ministry was actually Harry Potter in disguise. After the trio accidentally unleashed some Dementors, he followed them and tried to chase the trio. He was able to grab them when they left by the Floo Network, but he was dropped off when Hermione changed the location after she discovered that they were followed. As Yaxley was now aware of the location of Grimmauld Place, the trio was no longer able to use it as a hideout.
In the book he fights in the Battle of Hogwarts and he's present when Voldemort attacks Harry in the Forbidden Forest. Later he's either killed, arrested, or fled to avoid imprisonment.
- On the DVD version of Harry Potter and the Deathly Hallows: Part 1, Yaxley is seen in one of the deleted scenes where he enters the house of Hermione's parents. But nobody was home since Hermione casted a spell on her parents earlier to make them leave.