The 30-year-old actor will play a character named Troy, who has a "wild temperament" and is "charismatic with a cruel streak", reported The Wrap.
Sharman is joining the Walking Dead spin-off as a series regular.
"Fear the Walking Dead", which also stars Frank Dillane, Alycia Debnam-Carey, Mercedes Mason, Kim Dickens, and Cliff Curtis, among others, is currently filming its third season in Mexico.