Grumblethorpe is reportedly haunted by the spirits of British General James Agnew and a servant named Justina, who died from the yellow fever epidemic. The ghost of General Agnew is associated with a bloodstain in the front parlor where he died, and the presence of Justina is marked by the smell of fresh bread. Other reports include the sightings of children playing on the third floor. During the Battle of Germantown, Agnew was brought to the house after being wounded and bled to death on the parlor floor, leaving behind a distinct bloodstain. His spirit is said to linger, and a black mist is rumored to rise from the spot. Some believe his moans can be heard on the anniversary of his death. Justina, a former servant to the Wister family, succumbed to the yellow fever epidemic and died at the house. Her ghost has been seen by visitors and is associated with the smell of freshly baked bread. Her appearance in the girls' bedroom also served as an early warning of her death to the family. A former caretaker's friend claimed to have witnessed children playing on the third floor of the house. The children were said to reveal hidden objects.