Mama Day is filled with supernatural occurrences. The people of Willow Springs, who have inherited hoodoo traditions from their enslaved forebears, strongly believe in the supernatural. Towards the end of the novel, readers learn that George, one of the narrators, has been dead for fourteen years, yet Cocoa still communicates with him frequently.

Mama Day truly embodies the supernatural. She has a "gift" passed down from her great-grandmother, the enslaved Sapphira Wade. According to local legend, Sapphira was a "conjure woman" with remarkable powers: she "could walk through a lightning storm without being touched; grab a bolt of lightning in the palm of her hand; use the heat of the lightning to start the kindling going under the medicine pot.… She turned the moon into salve, the stars into swaddling cloth, and healed the wounds of every creature walking up on two or down on four." The bill of sale for Sapphira, which appears at the novel's start, notes that she "has served on occasion in the capacity of midwife and nurse, not without extreme mischief and suspicions of delving in witchcraft."

This language reflects the white world's view of Sapphira's abilities, but the novel aims to demystify and positively present Mama Day's powers. In Willow Springs, where the residents are descendants of slaves, magic and the supernatural are essential parts of daily life. Mama Day's gift is something to be respected and sometimes feared.

The novel makes a clear distinction between Mama Day's style of hoodoo and two other forms: Dr. Buzzard's deceit and Ruby's harmful practices. Mama Day uses her gifts for good, healing the sick, assisting in childbirth, and helping Bernice conceive. She finds "joy … from any kind of life" and sees her role as "bringing on life, knowing how to get under, around, and beside nature to give it a slight push." She works in harmony with nature to encourage growth, while Ruby uses spells, poisons, and herbal mixtures with graveyard dust to harm and drive insane the women she believes are after her man. Mama Day only resorts to killing when she calls lightning to strike Ruby's house in retaliation for Ruby poisoning Cocoa. Meanwhile, Dr. Buzzard's supposed healing remedies are fraudulent, mainly consisting of alcohol with no real medicinal properties. He also exploits the villagers' fears and beliefs in ghosts to sell his charms and talismans.

The detailed portrayal of Mama Day's practices underscores her vast knowledge of effective herbal remedies. She also uses her psychological insight, as seen when she helps Bernice by giving her black and gold seeds. These seeds do not possess supernatural powers but represent Bernice's negative feelings toward her mother-in-law and her hopes for her child. Naylor thus demystifies some of Mama Day's methods, showing that her seemingly supernatural abilities are natural extensions of her understanding of the "real" world.