Sulkin made his acting debut in the 2002 mini-series Doctor Zhivago. He subsequently starred in the comedy Sixty Six, as Bernie Rubens, alongside Helena Bonham Carter, Eddie Marsan and Catherine Tate. Sulkin also played the role of JJ in the Disney Channel comedy, As the Bell Rings, worked on a CBBC children sci-fi show The Sarah Jane Adventures (spin-off of Doctor Who), playing Adam in series 3 two-episode story The Mad Woman in the Attic.
Sulkin was on Disney Channel's Pass the Plate as Gregg from the UK. He had a recurring guest role on the Disney Channel series Wizards of Waverly Place, where he played Alex's love interest Mason Greyback he reprised his role in 4 episodes of season 3 and returned to the series in its fourth season, and through to its finale.
In 2010 he went to New Zealand making a Disney Channel film Avalon High, which premiered on 12 November 2010. In an interview with Kyle Martino, aired on Soccer Talk Live on the Fox Soccer Channel in the US, Sulkin announced that he was a fan of Arsenal.
Sulkin was on the Disney Channel's Friends for Change Games and was on the Yellow Team.  Sulkin posing with a fan in January 2012He reprised his role as Mason Greyback in The Wizards Return : Alex vs. Alex on Friday, 15 March on Disney Channel.
In 2012, Sulkin starred in the American teen drama series Pretty Little Liars as a recurring character, Wesley Fitzgerald, brother of Ezra Fitz.
In February 2013, it was announced that Sulkin would play Julian Fineman in FOX's television adaptation of Lauren Oliver's young adult novel, Delirium. On 8 May, it was reported that Fox has decided not to pick up Delirium.
Since 2014, Sulkin has starred in the MTV comedy Faking It. Sulkin portrays Liam Booker.
|2006||Sixty Six||Bernie Rubens|
|2009||The Heavy||Teen Two|
|2011||Camilla Dickinson||Frank Rowan|
|2012||White Frog||Randy Goldman|
|2015||A Mouse Tale||The Dark Rodent||Voice; Direct-to-DVD|
|2016||Don't Hang Up||Sam Fuller||Post-production|
|2016||Status Update||Derek Lowe|
|2002||Doctor Zhivago||Seryozha||Television miniseries (ITV)|
|2006||Pass the Plate||Himself|
|2006||Man on the Moon||Michael Aldrin||Television special (Channel 4)|
|2007–08||As the Bell Rings||JJ||Main role|
|2009||The Sarah Jane Adventures||Adam||2 episodes|
|2010||Avalon High||Will Wagner||Disney Channel Original Movie; main role|
|2010–12||Wizards of Waverly Place||Mason Greyback||Recurring role (seasons 3–4; 15 episodes)|
|2011||R. L. Stine's The Haunting Hour||Matt||Episode (season 1, episode 20): "The Perfect Brother"|
|2011||Get the Look||Himself|
|2012||Melissa & Joey||Haskell Davis||3 episodes|
|2012||Pretty Little Liars||Wesley Fitzgerald||Recurring role (4 episodes)|
|2013||The Wizards Return: Alex vs. Alex||Mason Greyback||Television special (Disney Channel); main role|
|2013||Delirium||Julian Fineman||Unsold television pilot|
|2014||A Daughter's Nightmare||Ben Woods||Television movie (Lifetime)|
|2014-present||Best Friend's Brother||Ryan Vega||
Recurring (Season 2 - 5)
Main (Season 6 - present)
|2014–2016||Faking It||Liam Booker||Main role|
|2016||Life in Pieces||Jake||Episode (season 1, episode 20): "Prank Assistant Gum Puppy"|
|2016||Young & Hungry||Rick|
|TBA||F-Unemployed||Lead role; also executive producer and co-writer|
Awards and nominations
|2015||Teen Choice Awards||Choice Summer TV Star: Male||Faking It||Nominated|