Walsh will guest star in multiple episodes, the network said at a meeting of the Television Critics Association - which, appropriately enough, was in Beverly Hills.
She'll be reunited with a few members of the old West Beverly High School gang. As previously announced, Jennie Garth will return as Kelly Taylor, now a school guidance counselor, and Tori Spelling will be back as Donna Martin, who owns a boutique.
Also back is Joe E. Tata, again playing Peach Pit cafe owner Nat.
In the original series, Walsh was last seen bound for London to study acting.
She became a "successful theater actress, splitting her time between London and New York," a CW release explained. She then found equal success as a theater director - and her old school asks her to return as a guest director.
The drama about two teenagers from the Midwest who move to California and enroll in West Beverly Hills High School debuts Sept. 2.
