A judge in Los Angeles ruled that the effort by the nuns to sell it to a restaurant owner instead of the singer was invalid, according to The Guardian.
The Roman Catholic convent belonged to the Sisters of the Immaculate Heart of Mary but had been agreed to be sold to Katy Perry by the diocese without their approval.
Some of the remaining nuns were not happy to go ahead with the sale after watching a selection of her music videos.
Perry became famous with tracks like 'I Kissed A Girl' and 'California Girls'.
Two of the remaining five nuns claimed they owned the convent and can chose who to sell it to. They wanted restaurateur Dana Hollister to own it.
The archdiocese filed a lawsuit last summer asserting that it had the final say over who could sell the property, not the nuns.
After months of disputes Perry's attorney said she was pleased with the ruling which means the pop star is able to buy the property for £10.25 million to use as a private residence.
Representatives for the nuns and Hollister did not comment.
Katy Perry, the daughter of a pastor, identifies as a Christian and has a Jesus tattoo on her wrist.