Malalai Kakar, 41, who led Kandahar city's department of crimes against women, was leaving home Sunday when she was killed, said Zalmai Ayubi, spokesman for the Kandahar provincial governor. Her 18-year-old son was wounded, he said.
The Taliban claimed responsibility.
Militants frequently attack projects, schools and businesses run by women. The hard-line Taliban regime, which was ousted in the 2001 U.S.-led invasion, did not allow women outside the home without a male escort.
President Hamid Karzai condemned the assassination, as did the European Union, which said it was "appalled by the brutal targeting" of Kakar.
"Any murder of a police officer is to be condemned, but the killing of a female officer whose service was not only to her country, but to Afghan women, to whom Ms. Kakar served as an example, is particularly abhorrent," the EU said in a statement.