The 16-year-old girl succumbed to the injuries while the minor boy suffered serious injuries in the crash. He has been admitted to All India Institute of Medical Sciences (AIIMS) Trauma Centre.
The girl's body has been sent for autopsy, following which the body would be handed over to the family members.
Both teenagers are neighbours and study in the same school.
The tragic incident occurred at South Delhi's posh Vasant Vihar, when the boy sneaked the Alto car out of his home and took his friend it for a joy ride, police said.