The trio, two 16-year-olds and a 17-year-old, face 74 charges including human trafficking, forcible confinement and procuring for prostitution.
A fourth teen girl faces similar charges involving one incident, but her trial will be held at a later date.
Police allege the girls used social media to befriend and lure nine girls, aged 13 to 17, to a home at a housing complex in southeast Ottawa.
None of the accused or the nine victims can be named due to provisions in the Youth Criminal Justice Act.
Clients were told teens were 'pimps'
When the trial left off in early May, several clients testified about their dealings with the accused during arrangements to have sex with some alleged teen victims.
The men told the court the three accused had called themselves "pimps."
Some of the alleged victims also detailed their experiences in court where claims included verbal, physical and sexual assault from the three accused.
There will be seven victims testifying in court out of the nine total.
The trial is expected to last until November with Judge Diane Lahaie presiding.