Officers were called by the ambulance service to reports of a man unconscious on Ilford Lane in Ilford on Tuesday night.
Despite the efforts of paramedics to save him, the man died at the scene.
It is the second fatal shooting of a teenager in London in a week. On Sunday, an 18-year-old was shot in the head in Barking, east London.
The man shot dead in Ilford has yet to be identified and a post-mortem examination will take place in due course.
A 19-year-old has died after being shot while sitting in a car in east London.