"I want to thank everyone for their understanding and co-operation, it's because of their commitment, we are now able to take this next step."
It comes after Victoria reached 28 days without any community COVID-19 cases late last week. New South Wales is expected to reach the same milestone on Friday.
Under the plan, travellers from Victoria and New South Wales will still need to complete a border pass and be forced to undergo a health screening on their entry into Western Australia.
It follows a similar approach taken when WA reopened to most Australian states and territories last month.
Health Minister Roger Cook acknowledged the pain the border closures had caused for some.
"Today is another important step which we hope will help many families to be reunited with their loved ones for the festive season."
The news has been welcomed by the state's tourism and hospitality industries. WA Tourism Council chief executive Evan Hall believes it will allow the state to finally compete with other holiday destinations on the east coast.
"It allows flights to be scheduled, events to be planned, and tourism businesses to take firm bookings,” he said.
Australian Hoteliers Association WA chief executive Bradley Woods proclaimed the announcement means "WA will officially be open for business".
The state will remain closed to South Australia for the time being, with an update on travel restrictions expected next week.
The changes come as WA recorded three new cases of COVID-19 overnight, all return travellers in hotel quarantine.
