Dinesh Kumar, a Class XI student, was walking along the railway track with a friend at suburban Vandalur on Sunday evening when the incident happened, police said today.
He tried to click a picture of himself with the speeding suburban train behind him when it ran over him, killing the teenager on the spot, they added.
The victim's body was sent for post-mortem and further probe was on.
The incident comes close on the heels of a man and a girl drowning in Arabian Sea in Mumbai recently.
Doctors have been warning that taking too many selfies could result in "Selfitis," which they describe as a mental disorder.