The Guardian Angels will start patrolling near the Columbia Heights Metro Station Monday after a beating last week.
The group is focusing on 14th and W streets, less than a mile south of the Columbia Heights Metro station.
The group says that its presence is designed to serve as a crime deterrent, but that it will make a citizen's arrest if needed.
John Ayala, head of the D.C. chapter, says several people asked the group to patrol the area.
Ayala says they plan to be there twice a week, for five to six hours.
Police say a 36-year-old man was beaten in the area last week after confronting another man over littering.