Mazzara, who replaced original showrunner Frank Darabont midway through Season 2, announced his departure last month when the show was renewed for Season 4, citing creative differences with AMC.
"Both parties acknowledge that there is a difference of opinion about where the show should go moving forward and conclude that it is best to part ways," AMC said in a statement at the time. "This decision is amicable, and Glen will remain on for postproduction on season 3B as showrunner and executive producer."
Gimple joined The Walking Dead in Season 2 and was promoted to Mazzara's No. 2 when Mazzara was bumped up.
The Walking Dead returns for the second half of Season 3 on Sunday, Feb. 10 at 9/8c on AMC.
Will you miss Mazzara?