The Poisoning Department was a section of St Mungo's Hospital for Magical Maladies and Injuries, dedicated to dealing with poisons. It was most likely located on the building's third floor, which dealt with venoms and plant poisoning. While visiting Xenophilius Lovegood on 30 December, 1997 and being offered Freshwater Plimpy soup, Ronald Weasley retorted under his breath that people probably request the recipe to show to this department.
- Harry Potter and the Order of the Phoenix (Possible appearance)
- Harry Potter and the Deathly Hallows (First mentioned)