Vacant and abandoned buildings pose significant challenges to the health and safety of communities. In 2011, the City of Philadelphia began enforcing its “Doors and Windows Ordinance,” which required property owners of abandoned buildings to install working doors and windows in all structural openings or face significant fines. Forest Service scientists at the Philadelphia Urban Field Station tested the effects of the new ordinance on the occurrence of crime surrounding abandoned buildings from January 2011 to April 2013. They found that these building repairs were significantly associated with citywide reductions in overall crimes rates, total assaults, gun assaults, and nuisance crimes. But some significant increases were seen in narcotics sales and possession as well as property crimes around repaired buildings, which could be due to increased reporting, although mechanisms were not directly tested. Doors-and-windows repairs offer a relatively low-cost method of reducing certain crimes in and around abandoned buildings. Cities with an abundance of decaying and abandoned housing stock might consider some form of this structural repair to their built environments as one strategy to enhance public safety.