Mr Harris, 21, allegedly enticed an underage boy to produce sexually explicit videos and photos of himself, the US attorney's office said.
According to court records, Mr Harris admitted to soliciting and receiving explicit images from the minor.
But a spokesperson for the star has denied the allegations.
Mr Harris was arrested on Thursday morning and later appeared in court in Chicago.
He did not enter a plea. A judge said a hearing would be held on Monday to determine if he will stay in custody or be released on bail, according to US media reports.