He was rushed to a hospital where his condition was still unknown late Friday night.
The boy was hit near the Barrington Metra station at about 6 p.m. Friday evening.
Barrington police said the boy suffered severe injuries when he was struck by the Metra train.
Metra trains were moving Friday night after being delayed throughout the evening rush hour. It was just after 6 p.m. when Train 656, headed inbound to Ogilvie Station, hit an 11-year-old boy on the tracks in Barrington.
"I wouldn't want to be the parents at the end of that phone call. My son is 10, that's close to 11," said witness Daniel Madigan.
"Our officer administered first aid along with a witness, the fire department arrived and treated the 11-year-old," said Barrington Assistant Police Chief David Dorn.
Another witness snapped a picture of the rescue effort. Police say the boy was transported by ambulance to Lutheran General Hospital.
"There are severe injuries, but we don't know the extent of those injuries right now," Dorn said.
"I came out here and saw 20-30 people looking at the tracks," Madigan said. "You can see firefighters looking under the train."
Metra officials say passengers were on the train that struck the boy. The accident stopped Metra traffic in both directions, delaying trains up to 90 minutes both ways.
"It was a little delay, but nothing we couldn't handle," said Metra rider David Aguado.
"Overall, it wasn't as bad as it could have been," said Betsy Zimmerman.
Many questions still remain about how it happened, whether the boy was alone or with other people.