Nicole Ethel McMillen, 41, of Irvine, was arrested Sunday morning.
Irvine police said McMillen had sexual contact or inappropriate physical contact with the victim at her home on multiple occasions over the last six weeks.
The boy's parents notified authorities of the alleged crimes.
McMillen was arrested and booked into the Orange County Jail on $50,000 bail.
She posted bail and was released about 4 p.m. Sunday. Detectives said they're working with the school district to make sure McMillen is not in contact with students.
Detectives said that though she is employed as a part-time aide, her employment was not related to the victim and was not a factor.
However, detectives said there may be more victims.
"This is a very serious case and obviously we're taking it seriously and investigated it as quickly as possible to bring it to an end and to ensure that there can be no further victims," said Irvine police Lt. Julia Engen.
Anyone with information is asked to call the Irvine Police Department at (949) 724-7124.
