A family member stopped by the house just before 7:30 p.m. EDT Monday and found the bodies, Louisville Metro Police spokeswoman Alicia Smiley said.
Investigators believe the woman killed her daughters then shot herself, Smiley said.
Jefferson County Deputy Coroner Bob Jones identified the mother as Hope Orwick, 35, who he said died of a gunshot wound to the head. The girls were Emily Orwick, 9, and Lindsey Orwick, 8.
Jones said both girls died of stab wounds but he couldn't say how many times they were stabbed. An autopsy was scheduled for Tuesday.
Two chaplains were at the scene Monday night, and Smiley said 15 or so family members gathered there. Police talked to relatives to see if they could help explain what may have led to the deaths.
Neighbor Mechelle Rockey, 48, told The Courier-Journal that she has lived across the street from the family for about six months. She said the two girls often played outside.
"They were the sweetest little girls," Rockey said. "They were cute as a button."
Neighborhood children were distraught over the girls' deaths, Rockey said.
"They all played together," she said.