Police said the crash happened in the South Chicago neighborhood's 8400 block of South Commercial Avenue just after 4:40 p.m.
An 11-year-old girl was on an electric scooter, going southeast, when she was involved in a crash on a #26 CTA bus, which was traveling south on Commercial Avenue.
The child was transported to Comer Children's Hospital in serious condition.
Further information was not immediately available.
This is a developing story. Check back with ABC7 for updates.