The ship's owner P&O told the news site that a crew member witnessed the woman fall over the side of the ship about 4pm AEST, 150 nautical miles west of New Caledonia.
"A crew member notified the bridge straight away and the 'man overboard' incident response was activated immediately," spokesman David Jones revealed in an official statement.
"In line with this response, Pacific Dawn turned around to follow the course it was on at the time of the incident."
At the moment, The Australian Maritime Safety Authority and New Caledonian authorities have sent out a call for nearby vessels to assist in the emergency search.
Other passengers said children that were near her also witnessed the devastating fall. The woman is reportedly travelling with her children, however, it is unclear if they were on the deck with her.
"She leaned over and the ship rocked in heavy seas — her husband tried to catch her but she slipped," one passenger shared on social media.
This is a developing story.