The man fled the scene of the shooting in the 2700 block of Laurelcherry Street around 6 p.m., police said. That street is in The Townes at Crabtree subdivision, near Crabtree Valley Mall.
The woman was treated and released at a local hospital. Officials described her injury as "very minor."
Investigators said they were not sure if the man intentionally shot his mother or if the gun went off accidentally during their argument.
Officers were conducting an active search for the alleged shooter and were processing a warrant against him.
Police withheld the names of the mother and son.