The small silver sedan hit the child in the 900 block of Peach Avenue shortly before 4 p.m., city spokeswoman Monica Zech said.
Medics took the boy to Rady Children's Hospital. The severity of his injuries was not immediately clear.
The motorist pulled over following the accident and was cooperating with police.
Officers closed a block-long stretch of the street to allow investigators to gather evidence, Zech said.