The show stars Elijah Wood as Ryan, a man who meets Wilfred (Jason Gann).
The rest of the world sees Wilfred as a dog, but Ryan believes that he is speaking to a man in a dog costume.
Entertainment Weekly says that Kaczmarek has now signed up to play a woman who gets into a car accident with Ryan.
Kaczmarek played Lois in Malcolm in the Middle and has appeared in shows such as Raising The Bar, Cybill and Hill Street Blues. She also provides the voice for Judge Constance Harm on The Simpsons.
Chris Klein and Rashida Jones have also signed up for roles in Wilfred, which is expected to premiere on FX this summer.
Watch a trailer for Wilfred below: