A crew member saw the woman fall over the side of the ship about 4pm yesterday, the ship owner claimed.
It is believed the woman went out onto the boat's deck because she was feeling ill when a large wave washed up onto the ship and washed her overboard while her husband was watching nearby.
Spokesperson David Jones said, 'A crew member notified the bridge straight away and the 'man overboard' incident response was activated immediately.
'In line with this response, Pacific Dawn turned around to follow the course it was on at the time of the incident.'
The Australian Maritime Safety Authority and New Caledonian authorities have issued a call for nearby vessels to assist in the search.