Close contacts will be redefined as a household member or intimate partner of a COVID-19 case or someone who had more than 15 minutes of maskless contact with a positive case or spent more than two hours in a small room.
Casual contacts will cease.
The isolation period will be cut from 14 days to seven days, while approved vaccinated travellers from interstate and overseas will be allowed to complete seven days of home quarantine.
PCR testing is still recommended, but rapid antigen tests will also be able to be used as diagnostic tool with a compulsory online registration system.
WA premier Mark McGowan said the new settings would help manage community transmission and minimise disruption in the community and to the economy.
"Western Australia is about to embark on its most challenging phase of the pandemic," he said.
"Unfortunately, these new protocols are not a sign of the pandemic ending - they signify the real impact of Omicron beginning in Western Australia."
Miners had called for the immediate change to isolation rules after more than 100 fly-in, fly-out workers were forced to isolate on mine sites last week.
