Walker began his career writing about film and comic books in the 1990s, publishing work on his website and the zine BadAzz MoFo, which he founded in 1996.

[6] Walker and Sanford Greene co-wrote the 2016 revival of Marvel Comics' Power Man and Iron Fist, which featured the characters of Luke Cage and Danny Rand.

[11] Through Solid Comix, he published original graphic novels such as Bitter Root, co-written with Greene and Chuck Brown, and The Hated.

[2] The Hated, which follows the bounty hunter Araminta Free through an alternate history of the post-Civil War United States, was acquired by Netflix in 2021.

[18] In 2024, Walker and Anderson will retell and illustrate Mark Twain's Adventures of Huckleberry Finn as a graphic novel titled Big Jim and the White Boy: An American Classic Reimagined.