Hundreds of people have attended the country's largest citizenship ceremony in Wanneroo.
Premier Colin Barnett welcomed the 751 people from 60 countries who became Australia citizens.
But as the Premier walked to the stage he was heckled by a person in the crowd who said: "What you're doing with the sharks is wrong."
Mr Barnett replied: "The great thing about Australia is we all can voice our opinion."
A record 17,863 people from 155 countries will make the pledge to become Australian citizens at 400 ceremonies across the nation as part of Australia Day citizenship ceremonies.
WA will welcome 3140 new citizens hailing from 89 countries at 58 ceremonies to be hosted today.
Assistant Minister for Immigration and Border Protection, Senator Michaelia Cash, said Australia Day provided an opportunity for all Australians to pause and reflect on the privileges and responsibilities of being a citizen.
"Australia Day is a time to remember how fortunate we are to live in such a wonderful country," she said.
"The fact that a record number of migrants will today be proudly accepting Australian citizenship is testament to the fact that we live in the best country in the world and continue to attract those who understand the immense opportunities that exist here."
In Wanneroo, thousands of people have turned out to mark the country's largest citizenship ceremony, with many brandishing Australian flags and donning hats and bow ties to mark the day.
For those like the Yimer family from Ethopia, it is also an opportunity to officially join the Australian family.
Tesfaye and Sara Yimer, who has been in Australia since 2009, love the lifestyle and say there are better opportunities for their five children.
More than 4.5 million people have chosen to become Australian citizens since the first citizenship ceremony was held in Canberra on February 3, 1949,