Six children and three adults died in Monday's blaze, and another child is in hospital fighting for life, according to fire officials.
A neighbour described firefighters sobbing as they carried children's bodies from the one-storey property.
An electrical malfunction in an air conditioning unit's power cord caused the living room fire, said officials.
It is the most deaths from a single fire in the city since the 1920s, they added.
The breakdown of the death toll was changed after it was earlier announced that five children and four adults had died.
Most of the victims were pronounced dead at the scene in south Memphis.
Two other children died after being transported to Le Bonheur Children's hospital.
The children ranged in age from three to 17, family members told the Commercial Appeal.
"I've never seen firemen cry, but they were bawling like babies when they brought the children out," neighbour Shondra Hampton told the newspaper.
Some of the victims had signs of smoke inhalation, while others had burns, said Memphis fire services.
Fire Department Lt Wayne Cook said first responders arrived at around 01:30 local time.
It took them 15 minutes to extinguish the flames and remove the victims from the home.
The fire began in the living room and only consumed about a fifth of the building, said fire officials.
But smoke spread throughout the home.
Investigators determined the house did have a working smoke alarm.
But metal bars cover all the windows, and may have prevented the victims escaping.
"Our whole city is in mourning for the loss of much of one family," said Memphis Mayor Jim Strickland.
"It's a very sad day."
A house fire has killed nine people in Memphis, Tennessee, in the city's worst such tragedy in an almost century.