Robert Kazinsky was born Robert John Appleby in Haywards Heath, Sussex, England, to Phyllis and Paul Appleby, and grew up in the seaside town of Brighton, on England's southern coast. Both of his parents are from Polish Jewish/Russian Jewish families.
Kazinsky studied theatre at the Guildford School of Acting from 2002-2005 graduating with full honors, shortly thereafter he was cast as the enigmatic footballer Casper Rose in Sky One's footballing drama Dream Team, he only starred in one season but his character was received so well that he won that seasons most popular character poll with a whopping 54.29% of the vote.
After announcing his intention to leave in 2006, Kazinsky was cast as the disturbed and dangerous ex-military ladies man Sean Slater in EastEnders. In his 254 episodes Rob was nominated for 23 awards winning 7 including two Best Actor Awards culminating in his triumph at the British Soap Awards in 2008.
In 2010 after guest stints on Law and Order: Los Angeles and ABC's Brothers & Sisters, Kazinsky was announced to be playing Fili in Peter Jackson's The Hobbit due to start filming in 2011.
In 2012 it was announced he would join the cast of the sixth season of the US television fantasy drama True Blood in 2013. In 2013, Kazinsky appeared in the Guillermo del Toro film Pacific Rim, as Chuck Hansen, an Australian Jaeger pilot.
In 2015, he portrayed Guy in the science fiction film Siren. He was cast in the leading role in the U.S. Fox drama series Second Chance. His character, James "Jimmy" Pritchard, was a murdered elderly ex-cop who is genetically brought back to life as a man in his mid-30s with unusual powers. The series debuted in early 2016.
Kazinsky co-starred as Orgrim Doomhammer in the Warcraft film adaptation, which was released in May 2016.