The Calgary woman, who is in her early 30s, will be tried on an attempted murder charge at a later date.
Charges were laid against Borowiec after a baby was found alive in a dumpster near her house in 2010. While being interrogated by police, she told them she had previously abandoned two other babies in dumpsters.
Borowiec, who was being tried on two counts of second-degree murder, nodded as Court of Queen's Bench Justice Peter McIntyre read the infanticide verdict on Tuesday afternoon.
During a police interview, Borowiec said she had given birth to babies in 2008 and 2009. She said in both cases she wrapped the babies in a towel, placed them in a garbage bag and put them in a dumpster.
Their bodies were never recovered.
She said that in all three cases case she hid the pregnancy from her longtime partner.
In July 2012, while in custody at the Southern Alberta Forensic Psychiatric Centre, Borowiec gave birth to a fourth child. That baby, a boy, was given up for adoption.
Borowiec will remain on bail pending sentencing.