Movies:
* The Last Witch Hunter (2015) as Dolan
* The Wolfman (2010) as Young Gwendel
* The Other Boleyn Girl (2008) as Henry Fitzroy
* The Children of Men (2006) as News Reporter
* The Libertine (2004) as Lord Rochester (young)
* Bright Young Things (2003) as Freddie
Television:
* The Tudors (2007-2010) as Thomas Culpeper
* The Borgias (2011-2013) as Cesare Borgia
* The Last Kingdom (2015-2022) as Æthelred
* Ripper Street (2012-2016) as Sergeant Bennet Drake
* Black Mirror (2013) as the young father in the episode "White Bear"
* Silent Witness (2000) as Kevin
This is not an exhaustive list, but it highlights some of Michael Atha's most notable roles. He has also appeared in other TV shows and films, and continues to work in the entertainment industry.