Kazinsky was born in Cuckfield, Sussex, England and grew up in the seaside town of Brighton on England's southern coast. Kazinsky studied theater at the Guildford School of Acting for three years and graduated with honors. In 2005 he starred in the BBC One drama Dream Team for one season; however, the reception of the character was positive enough that he eventually returned for another season. After leaving Dream Team in 2006, he was later cast in EastEnders as Sean Slater, a "disturbed" ex-military man. The role as Slater earned him over twenty-three nominations. He won seven of them, two of them Best Actor nominations.