The former "Will & Grace" star will have a recurring role on "Christine," starting this fall when the series returns for its fifth season.
The network said McCormack will play a therapist who shares office space with Christine's brother, Matthew, played by Hamish Linklater, and begins a "complicated therapist/love interest relationship" with Christine, who is played by Julia Louis-Dreyfus.
McCormack's stint on the show reunites him with Kari Lizer, who was a writer and co-executive producer on "Will & Grace." Lizer is the creator and executive producer of "Christine."
McCormack's other television credits include "Trust Me," "The Andromeda Strain," "Dead Like Me," "Ally McBeal" and "The Outer Limits."