Chief prosecutor Miguel Matias told the AP all seven defendants were found guilty of crimes including sexually abusing minors and adolescents, raping children and running a pedophile ring at a state-run children's home in Lisbon during the 1990s.
Matias, speaking during a lunch break on the trial's final day, said the court was due to hand down sentences later Friday. He could not immediately provide a breakdown of the crimes the court ruled were proven.
All defendants have the right to appeal.
The trial, believed to be Portugal's longest, included testimony from more than 800 witnesses and experts, including 32 alleged victims, and shocked the country.
The abuse centered on Casa Pia, a 230-year-old institution caring for roughly 4,500 needy children, most of them living in dormitories at its premises around the capital.
The defendants include a national television celebrity and a retired ambassador in a case that shook public trust in the country's institutions when the allegations emerged in 2002.
Ana Peres, the lead judge in a three-judge panel, read a summarized version of the court's decisions, some of which was televised. The full document reportedly stretches to almost 2,000 pages.
The victims - now aged between 16 and 22 - have given chilling testimony during the trial and identified their alleged abusers by pointing to them across the courtroom.
"Some of the accounts could be considered pornographic," Peres told the small courtroom where a few members of the public were present.
A 53-year-old former driver at the Casa Pia, Carlos Silvino, confessed to more than 600 crimes and incriminated the other defendants.
They include Carlos Cruz, a popular television presenter with a three-decade career in show business, and Jorge Ritto, a decorated career diplomat and former UNESCO ambassador. Three other men are also charged with child sex abuse, including a doctor and a former Casa Pia ombudsman. A 68-year-old woman, Gertrudes Nunes, is charged with providing her house for meetings between the children and the alleged pedophiles.
The six denied the charges and said their lives have been ruined by the allegations.
The former ombudsman, Manuel Abrantes, said the allegations wrecked his career and family life.
"My life was destroyed overnight," he said.
The claims that a pedophile ring had preyed on children at the state institution for years rocked the public's faith in the authorities, who appeared unable to protect the most vulnerable members of society.
The protracted trial has also fueled outrage about Portugal's notoriously slow legal system.