Discovered in 2003 after going through his first major audition, he landed a role on the ABC teen drama Life As We Know It. Of the show's trio of male characters, Lowell portrayed Jonathan Fields, the "least confident but most creative and grounded of the three". The series was cancelled after 13 episodes.
In 2006, Lowell had lead roles in the coming-of-age film Graduation and also in a small film entitled You Are Here.
From 2007 until 2010, Lowell appeared in the ABC drama Private Practice, alongside Kate Walsh, Audra McDonald, and Tim Daly, playing Dell, the receptionist for the Oceanside Wellness Group who is also a qualified nurse, midwife-in-training, and young father to six-year-old daughter Betsy. Lowell exited Private Practice in the show's third-season finale when Dell died from heart failure, a complication during brain surgery after a vehicle accident.
In 2011, Lowell played the role of Stuart Whitworth in the film The Help, an adaptation of Kathryn Stockett's 2009 novel of the same name. The following year, filming began on Lowell's directorial debut, Beside Still Waters. Set in Michigan’s Upper Peninsula, the film tells the story of a man redefining his outlook on life after the death of his parents.
Lowell also played Derrick on Fox's 2014 comedy, Enlisted.
