It happened around 1 a.m. Wednesday on the 200 block of North Rodney Street.
Officers arrived to find a 33-year-old man shot in the torso and legs.
Medics treated him at the scene, then rushed him to Christiana Hospital in critical condition.
Police say shell casings were found over a two-block area.
They are working to determine who shot the man and why.
Anyone with information about the incident is asked to call Wilmington Police Detective Jose Santana at 302-576-3972.