The Reversing Spell is, as described in a spellbook at Cackle's Academy, a simple spell that will fix most things. It's incantation is "reversus revolvus, returnus resolvus, ilio-alio, redux reducio." In order for it to work right, every word must be spoken correctly. When the spell is mispronounced, it may result into turning the person into something different instead. This reversing spell is often used to reverse transformation spells.
- Charlie Blossom tried to use this spell on Ethel Hallow, who had been turned into a pig. He turned her into a duck instead. With the help of Mildred and her friends, he later managed to cast the spell correctly.
- Ethel then turned Charlie into a donkey. She didn´t know the reversing spell, and the other students cast it. (A Pig In a Poke)
- Miss Constance Hardbroom used this spell on a monkey, believing it to be Ethel Hallow. It turned out to be Enid Nightshade's cat instead.(Monkey Business)
- Ethel Hallow uses this spell to turn Mildred, whom she had turned into a frog, back to human form. (It's a Frogs Life)
- Maud Spellbody cast this spell to reverse a statue transformation spell cast on Mildred Hubble. (Art Wars)