Before getting into acting, Welling was a high school athlete then a Fashion Model. He has also been involved behind the camera as an executive producer and a director; he directed seven episodes of Smallville and became one of the show's producers in its last two seasons. He also produced the short-lived Hellcats.
- Judging Amy (2001) as Rob Meltzer
- Special Unit 2 (2001) as Victim
- Undeclared (2001) as Tom
- Smallville (2001-2011) as Kal-El / Clark Kent / The Blur / Superman
- Cheaper by the Dozen film series (2003, 2005) as Charlie Baker
- The Fog (2005) as Nicholas "Nick" Castle
- Draft Day (2014) as Brian Drew
- Lucifer (2017-2018) as Marcus Pierce / Cain
- Irony as She Is Cast: Like Christopher Reeve, he was not a big Superman fan prior to being cast as the character on Smallville, and in fact continues not to read Superman comics after the show ended.
- Mr. Fanservice: His characters were huge hits with the female (and even male) audience.
- Star-Making Role: Playing the pre-Superman Clark Kent on Smallville made him a household name.
- What Could Have Been: