A woman in a toilet cubicle at a cinema in Sydney's CBD has detained a teenager who was allegedly filming her from the neighbouring stall.

The 47-year-old woman said she saw a hand holding a phone underneath the cubicle partition, according to police.

She stomped on the 15-year-old boy's hand and phone, and trapped the boy inside the adjoining cubicle until security apprehended him.

Police arrested the boy and found in his bag another mobile phone, which allegedly had videos of other women filmed in bathrooms.

The phone was seized to be examined further by forensic officers.

The teenager was charged with five counts of filming a person in a private act without consent.

He was refused bail and is expected to appear at a children's court later.