Investigators found that the patients, all seriously but not terminally ill, died as a result of being administered strong doses of the anticoagulant drug Eparina by nurse Fausta Bonino.
Bonino was accused of giving the fatal doses of the blood-thinning drug to patients in intensive care at a hospital in the Tuscan town of Piombino between January 2014 and September 2015.
She was arrested in 2016 after a review of abnormal deaths at the hospital identified her as being the only staff member involved in every case.
Bonino, 56, protested her innocence amid tears on Friday after the voluntary homicide verdict was delivered.
The nurse’s lawyer said she would appeal her sentence.