O'Connor, known for her stirring voice, outspoken views and 1990 chart-topping hit "Nothing Compares 2 U", was pronounced dead at the scene. Police had said her death, at the age of 56, was not being treated as suspicious.
The coroner's court said at the time that an autopsy would be conducted before a decision was made on whether to hold an inquest.
"This is to confirm that Ms O'Connor died of natural causes. The coroner has therefore ceased their involvement in her death," London Inner South Coroner's Court said in a statement.
Artists around the world reacted to the news of her death last year, with REM frontman Michael Stipe and U.S. musician Tori Amos among those who paid tribute to O'Connor's fierce honesty, intense presence and uncompromising spirit.
Thousands gathered outside O'Connor's former seaside home to bid farewell to her when her funeral was held in August, some singing along to hits blasted from a vintage Volkswagen camper van and others showering her hearse with flowers.
