Gregg was born in London, England where he attended Highgate School.
He made his acting debut in 2002, with the mini-series Doctor Zhivago. Gregg recently played the lead role of Will Wagner in the Disney Channel Original movie "Avalon High", which premiered on November 12th, 2010.
Currently, you can see him in his recurring role of Alex Russo's werewolf boyfriend, Mason Greyback on the Disney Channel Original series Wizards of Waverly Place & ABC Family's "Melissa & Joey". He has two feature films currently in post production; "Camilla Dickinson" and "White Fog".
Last month, Sulkin recieved the "Rising Star Award" at the Hawaii International Film Festival 2011 in Honolulu.
He has just now started work on ABC Family's Pretty Little Liars where he is playing the role of Wesley Fitzgerald.