Hilton Cordero Rosario is expected to serve 10 years in prison as a result of Friday's plea. His sentencing is scheduled for June 10.
Cordero was accused of convincing his teenage daughter's friend to expose her genitals and of taking pictures of her. Authorities also said they had seized a computer belonging to him with graphic images of other minors.
Defense attorney Melanie Carrillo told reporters that the case had been tried in the media and Cordero wasn't given a chance to share his version of events.
Cordero was arrested in April 2011.