How Do Opossums Get into Walls? When there are opossums in the walls of a home, they likely got there by climbing a tree near the residence. Trimming branches that touch the house can prevent invasion, as well as wrapping the bottom two feet of the trunk with metal flashing. Health Risks Having an opossum in the wall poses a health danger to people in the home. The pests can carry many diseases, plus the fleas and other parasites in their fur are vectors for even more. Opossum nesting habits also generate unpleasant odors, and the pests may discharge a foul-smelling fluid when frightened. Prevention Conducting annual inspections of a home's exterior is a good step to keep opossums and other wildlife from getting indoors. Other preventive actions homeowners can take include: Plugging any gaps along the foundation Covering vents with metal vent covers Attaching metal flashing or quarter-inch hardware cloth to protect other openings that must be maintained for airflow or exhaust After finding opossums in the walls or other parts of the house, contact Critter Control for safe, professional removal.