Ultimately, Kleintank went to New York City to pursue his acting career, and made his television debut as Greg in a 2009 episode of Law & Order: Special Victims Unit. In 2010, he played a recurring role in Gossip Girl as Elliot Leichter, a bisexual love interest for Eric van der Woodsen. Kleintank landed his first daytime role that same year, debuting as Noah Newman in The Young and the Restless on September 21, 2010; however, he left the role after less than six months.
In 2011, Kleintank joined the recurring cast of the Fox series Bones, playing Finn Abernathy. He has also appeared multiple times in the CBS series The Good Wife. From 2013 to 2014, Kleintank portrayed the recurring character of Travis in the ABC Family teen drama series Pretty Little Liars. In 2015, Kleintank was cast as Joe Blake in the Amazon series The Man in the High Castle.