Macken has modelled for Abercrombie and Fitch, Ralph Lauren, and GQ, and has appeared in films such as Resident Evil, Close, Killing Jesus, and Centurion.

In addition, Macken has directed several feature films: Christian Blake in 2008, Dreaming for You, The Inside and Cold, and Here Are the Young Men.

[2] He also appeared in the role of drug dealer Gavin Cluxton in several episodes of the TV series Fair City in 2008.

[12][13] In 2009–10, Macken had roles in the BBC drama Small Island (playing an American soldier named Calhoon), in Neil Marshall's film Centurion, and in the second series of RTÉ's Raw.

[14][15] Between 2010 and 2012, Macken played the recurring character of Gwaine (loosely based on the image of Gawain) in the BBC One TV series Merlin.

Drawn back together by the unexpected death of their father, they are immediately at odds with each other until they find a girl dumped in the moors.