Parker is most famous for his role as Haldir of Lórien in The Lord of the Rings movie trilogy and his performance of Bellerophon in the universally famous show Xena: Warrior Princess. He also does voice-overs for New Zealand documentaries and has been entertaining and meeting fans at various Lord of the Rings-related conventions for several years - for example, Ring*Con in Germany, which he has attended every year since its creation in 2002, with the exception of 2007, when he had to cancel his appearance due to pressing acting commitments. His recent work has also involved voiceover work in the recent Power Rangers series since the filming moved to New Zealand. He is currently starring in the TVNZ soap Shortland Street, as Guy Warner, from which his character has been absent for 11 years. He has an older brother named David, and he also has an older sister. He is the reigning champion of New Zealand's Celebrity Joker Poker.

Parker currently stars as Darken Rahl in Sam Raimi and Rob Tapert's syndicated television series Legend of the Seeker, he also appears as Gaius Claudius Glaber in the Starz original series Spartacus: Blood and Sand which premiered on 22 January 2010 and is also produced by Sam Raimi and Rob Tapert.

Parker currently stars as Darken Rahl in Sam Raimi and Rob Tapert's syndicated television series Legend of the Seeker, he also appears as Gaius Claudius Glaber in the Starz original series Spartacus: Blood and Sand which premiered on 22 January 2010 and is also produced by Sam Raimi and Rob Tapert.