A third season of Warehouse 13 was announced by SyFy on October 5, 2010.
This comes on the heels of an average 3.4 million U.S. viewers for each episode of Season 2, making it SyFy's most watched series. 
- Eddie McClintock as Peter Lattimer (13 episodes)
- Joanne Kelly as Myka Bering (13 episodes)
- Saul Rubinek as Arthur Nielsen (13 episodes)
- Genelle Williams as Leena (7 episodes)
- Allison Scagliotti as Claudia Donovan (13 episodes)
- Aaron Ashmore as Steve Jinks (10 episodes)
- CCH Pounder as Irene Frederic (6 episodes)
- Anthony Micheal Hall as Walter Sykes (6 episodes)
- Ashley Williams as Sally Stukowski (5 episodes)
- Sasha Rioz as Marcus Diamond (6 episodes)
- Jaime Murray as Helena G. Wells (4 episodes)
- Kate Mulgrew as Jane Lattimer (4 episodes)
- Faran Tahir as Adwin Kosan (3 episodes)
- Max Morrow as Tyler Struhl (3 episodes)
- Paula Boudreau as Theadora Stanton (2 episodes)
- Lok Archer as Lok Archer (2 episodes)
- Lindsay Wagner as Vanessa Calder (1 episode)
- Rene Auberjonois as Hugo Miller (1 episode)
- Jeffery R. Smith as Mr. Keeler (1 episode)
- Roger Rees as James MacPherson (1 episode)
|The New Guy||Writer: Jack Kenny||Director: Stephen Surjik||July 11, 2011||#1|
|A new agent replaces Myka as Pete's partner, and artifacts from Warehouse 2 cause trouble while they're being unpacked.
|Trials||Writer: Drew Z. Greenberg||Director: Constantine Makris||July 18, 2011||#2|
|Pete and Myka investigate why people are losing their memories, while Claudia and Steve go to an auction to get a knife that allows for transfer of disease and injury.
|Love Sick||Writer: Andrew Kreisberg||Director: Tawnia McKiernan||July 25, 2011||#3|
|Dr. Calder calls on Artie to assist in stopping a dangerous virus of unknown origin. Meanwhile, Pete and Myka find themselves in a strange situation which is complicated by Steve's disappearance. In order to find Steve they must recover their memories and retrace their steps.
|Queen For A Day||Writer: Holly Harold||Director: Jeremiah Chechik||August 1, 2011||#4|
|Pete's ex-wife Amanda visits Univille and inadvertently comes into contact with an artifact. Claudia and Steve are on the trail of an artifact connected with the American Civil War.
|3... 2... 1||Writer: Bob Goodman||Director: Chris Fisher||August 8, 2011||#5|
|The hunt for an artifact involves three teams of agents, 108 years, two incarnations of the Warehouse, and two continents.
|Don't Hate The Player||Writer: Ian Stokes||Director: Chris Fisher||August 15, 2011||#6|
|Claudia and Pete have to rescue Fargo from a video game he made based on the Warehouse, while Jinks and Artie team up with Stukowski to snag a Van Gogh that tends to kill people.
|Past Imperfect||Writer: Nell Scovell||Director: Tawnia McKiernan||August 22, 2011||#7|
|Claudia and Jinks are ambushed while attempting to recover an artifact and must uncover the assailant's identity. While on assignment in Denver Myka crosses path with the man who murdered Sam, allowing Pete and Myka to uncover the truth about Sam's murder.
|The 40th Floor||Writer: Benjamin Raab & Deric A. Hughes||Director: Chris Fisher||August 29, 2011||#8|
|After capturing Sally Stukowski the Warehouse Agents learn her assignment is to assassinate several of the Regents meeting in Atlanta. The team is forced to exceed their mandate to protect the Regents leading to a series of unforeseen consequences and revelations.
|Shadows||Writer: Bob Goodman & Holly Harold||Director: Tawnia McKiernan||September 12, 2011||#9|
|As Pete and his mom explore her subconscious for information on A-Z Technologies, Claudia and Myka investigate an artifact that is killing people when a girl named Megan gets angry.
|Insatiable||Writer: Benjamin Raab & Deric A. Hughes||Director: Constantine Makris||September 19, 2011||#10|
|Myka and Pete chase an artifact that seems to turn people into zombies, while Claudia tries not to be killed by an artifact while attempting to join a band.
|Emily Lake||Writer: Nell Scovell & Ian Stokes||Director: Millicent Shelton||October 3, 2011||#11|
|Sykes is getting closer and closer to his endgame, while the agents look for information to get ahead of him. What they find is an old friend, but not quite the same person she was...
|Stand||Writer: Andrew Kreisberg & Drew Z. Greenberg||Director: Stephen Surjik||October 3, 2011||#12|
|Fueled by grief, Claudia, Myka, and Pete work harder than ever to bring Sykes down, and avenge the death of their friend before their most dangerous enemy yet completes his endgame and destroys the Warehouse.
|The Greatest Gift||Writer: Jack Kenny||Director: Mike Johnson & John-Paul Nickel||December 6, 2011||#13|
|While Pete is placing an artifact in the Christmas Aisle, several artifacts fall on him, including one that transports him to a reality where he doesn't exist. Now, he has to find a way to get back to his reality.