The incident occurred at around 12pm Australian Western Standard Time, the company said. It informed the market just before 5pm today, several hours after the market closed.
Energy News has been informed the contractor worked for rope access company Vertech.
The company was contacted but offered a ‘no comment' at this point.
Rope access deaths in the oil and gas industry are relatively uncommon.
A full analysis of the incident will take over a week.
"This is a very sad day for the extended Woodside family and I offer my deepest sympathy to our colleague's family, friends and workmates," CEO and managing director Meg O'Neill said.
"Any loss of life is heartbreaking.
"We are taking all steps to understand the circumstances around this tragic event and are cooperating closely with Western Australian Police and the National Offshore Petroleum Safety and Emergency Authority in their ongoing investigations."
The North Rankin facility feeds the North West Shelf LNG facility, which exports product to Asia.
In mid-2021 the National Offshore Petroleum Safety and Environmental Management Authority issued Woodside a General Director to ensure the caissons at the facility were "safe and without risk to health".
"Structural integrity failure of one or more of the remaining caissons at the NRA platform could lead to dropped object damage to the facility structure or loss of containment from the subsea gas and condensate pipelines, which may result in a major accident event," NOPSEMA said then.
The direction was marked as closed later that year.
"A team of experienced investigators have been mobilised to attend the scene and a do not disturb notice has been issued to the operator. NOPSEMA is working with other relevant authorities as appropriate," a NOPSEMA spokesperson said.
This story has been updated to reflect a response from NOPSEMA.
More to come.