Born Markell V. Efimoff in Everett, Washington, Young began acting at the age of 9 and moved to Los Angeles when he was 12 to pursue his career. His first significant on-screen credit was a small role in two episodes of the HBO series Six Feet Under.

Young's other notable appearances include television shows The OC, Dexter, Big Love, Childrens Hospital, Heroes, Secret Life of the American Teenager, Cold Case, ER, CSI: Crime Scene Investigation and The Inbetweeners, while his film credits include Sex Drive, Happiness Runs, a turn as Tim Robbins' character's son in The Lucky Ones, and We're the Millers, a comedy starring Jennifer Aniston, Emma Roberts, Will Poulter, Jason Sudeikis, Ed Helms, and Nick Offerman.