Below is a list of television that Glenn Howerton has starred in. They are listed in reverse-chronological order, with the most recent ones last. Click on the titles to read more about each project individually.
| 2002 | The Job | Young guy |
| 2002 | That ’80s Show | Corey Howard |
| 2003 | ER | Dr. Nick Cooper |
| 2005-present | It’s Always Sunny in Philadelphia | Dennis Reynolds |
| 2009 | American Dad! | Animal control guy #1 (voice) |
| 2009-2010 | Glenn Martin, DDS | Various voices |
| 2009-2013 | The Cleveland Show | Ernie Krinklesac / various voices |
| 2011 | Vietnam in HD | Donald DeVore |
| 2012 | Unsupervised | Clint / Dirt (voices) |
| 2013-2017 | The Mindy Project | Cliff Gilbert |
| 2014-2015 | Family Guy | Various voices |
| 2014 | Fargo | Don Chumph |
| 2015 | TripTank | Congressman Rothbard, Hume, and Adorno (voices) |
| 2016 | House of Lies | Seth Buckley |
| 2017 | A.P. Bio | Jack |