The law requires children 11 and under to be off the streets by 8:30 p.m. Sunday through Thursday and by 9 p.m. Friday and Saturday.
The curfew for children between the ages of 12 and 16 is 10 p.m. Sunday through Thursday and 11 p.m. Friday and Saturday.
Mayor Rahm Emanuel handed out cards at a CTA Red Line station in the Uptown neighborhood Friday to remind parents about the new law.
"It's part police work, but it's parental responsibility you cannot replace," Emanuel said. "Law enforcement cannot replace what parents need to do and are responsible to do. Make sure ordinances back up responsible parenting."
A three-strikes penalty system is now in place. Police will assess a $500 fine for the first two violations and $1,500 for the third.