The 42-year-old was suing Joyleen Robinson in the Victorian Supreme Court for full ownership of two properties bought as a result of her success.
One was an eight-hectare property in Narre Warren in Melbourne's southeast, while the second was Amorosi's current residence in California.
Amorosi claimed the $650,000 used to purchase the Narre Warren home in 2001 came from a trust account set up to receive all of her earnings as a singer-songwriter.
Amorosi sued mother Joyleen Robinson (centre) in the Victorian Supreme Court (James Ross/AAP PHOTOS)
Mrs Robinson alleged Amorosi agreed to hand over full ownership of the Narre Warren home if she paid $650,000 when asked.
She maintained the agreement was made in February 2001 during a conversation in the kitchen of their former family home.
Mrs Robinson said she handed over $710,000 to Amorosi in 2014 for the loan she took out on her American home, maintaining she fulfilled her end of the housing pact.
But Amorosi told the court she should have full ownership as there was never any agreement in place.
The singer also sought to be the sole owner of her current Californian residence, which was bought through a trust account set up by her mother.
Justice Steven Moore on Thursday ruled the supposed agreement between Amorosi and her mother never happened and the Narre Warren property should be under Amorosi's name alone.
He also found that Amorosi should be the sole owner of her Californian home.
But Justice Moore did agree that Mrs Robinson should receive restitution from Amorosi for the contribution she made to Amorosi's property in 2014.
He ordered Amorosi pay her mother $650,000 plus $219,486.33 in interest.
Amorosi did not attend court on Thursday for Justice Moore's judgment as she was still in the US.
Mrs Robinson was also not in attendance, although some of her family members watched on in court.
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