Wide Sargasso Sea is most often put into the genre of the postcolonial novel. Postcolonial literature tells a story from the point of view of the subaltern or oppressed other, usually the person or peoples being colonized or taken over by a more powerful group.

In Wide Sargasso Sea, Antoinette represents the colonized other. Growing up almost wild, a child of nature in the lush West Indies, she is married to and oppressed by Rochester, a second son who wants her for her fortune and despises her for being a Creole. He has no interest in or understanding of her culture or desires, but crushes her instead, framing her cultural differences as insanity. The book reframes Jane Eyre from the perspective of the "view from below," the despised person in the original novel given a voice to tell her own story.

The novel is also post-colonial in taking an unflinching look at slavery and its aftermath in the West Indies and exposing the cruel foundation of much of British wealth.