The 38-year-old woman stabbed her 18-year-old son several times around 10 pm, police confirmed.
The teen's two younger sisters alerted emergency services, but they arrived too late. Their brother suffered a deadly wound to the heart and died at the scene.
The woman and her son, who worked as a floor tiler and still lived with her in the Harlaching district apartment, were known to have had violent arguments in the past.
Police arrested the mother in the apartment.
Munich authorities plan to release more information on the murder on Monday afternoon.