The court in the northern city of Brescia sentenced each of the three to 30 years in prison for the slaying of Hina Saleem, the ANSA and Apcom news agencies reported.
In addition, the girl's uncle was convicted of helping hide her body. He was sentenced to two years and eight months.
Saleem's body was buried in a hole dug in the family's garden in the town of Sarezzo last year. Prosecutors alleged the three men killed her because she dated an Italian man and refused to conform to an Islamic lifestyle.
In Italy, convictions are not considered final until the two levels of appeals have been exhausted. Defense lawyers weren't immediately available to comment on whether they planned to appeal.
Loredana Gemelli, a lawyer representing the Italian man who was dating Saleem, told reporters outside the Brescia courthouse that the murder was not an honor killing. "It was a punishment that (the father) wanted to inflict on Hina," she said.
Saleem's mother, Bushra Begun Saleem has said her daughter was disobedient, often staying out late without saying where she was or when she was coming home. She has also said she did not forgive her husband for his participation in the killing.
The mother had left for Pakistan before the slaying and flew back after she learned the news. She was taken from the courthouse in an ambulance on Tuesday, after shouting incoherently after the convictions were read out.