Australia's most famous landmark was lit up with the silver fern as a symbol of solidarity with New Zealand.
At 8.30pm, the sails of the Sydney Opera House shone bright with the iconic frond of the tree fern.
NSW Premier Gladys Berejiklian announced earlier yesterday that Australia would pay tribute to those lost in the Christchurch terror attack with the small gesture.
• The faces of the victims
"The Silver Fern of New Zealand will be displayed on Sydney Opera House tonight — a symbol of solidarity, support and respect for the people of New Zealand," she wrote on Twitter.
"Our thoughts and prayers go out to all those impacted by the tragic events in Christchurch."
Later, she tweeted a picture of the light display with the words: "In unity, with all our love."
It comes after 49 New Zealanders were murdered during Friday prayers at two mosques in Christchurch.
The suspect, from Grafton in NSW, has been charged with one count of murder but further charges are expected.
The 28-year-old right-wing extremist filmed himself on the rampage before he was arrested and charged.
During a brief, three-minute appearance in court, the former fitness instructor did not request bail and was taken into custody until his next court appearance, which is scheduled for April 5.
Thoughts and prayers are being sent to Christchurch from around the world as locals come to grips with a terror attack in their backyard that killed a 2-year-old boy and a 4-year-old girl, among dozens of others.
Australian Prime Minister Scott Morrison spoke with reporters in Sydney's southwest today. He told media outside Lakemba Mosque that Australia sends its "profound and deepest condolences and sympathies for the horrific and tragic terrorist attacks that took place in New Zealand".
"Its important to be here standing with you because as Prime Minister Jacinda Ardern said yesterday, an attack against one is an attack against all of us," Morrison said.
"From all communities who love peace, who love the freedoms that we have both here in Australia and New Zealand and the peace loving peoples of the world. This is what is under attack."
The Queen and British government leaders have sent condolences and expressed their sadness.
In a message to the Governor-General of New Zealand, the Queen said: "I have been deeply saddened by the appalling eventsin Christchurch today. Prince Philip and I send our condolences to the families and friends of those who have lost their lives.
"I also pay tribute to the emergency services and volunteers who are providing support to those who have been injured. At this tragic time, my thoughts and prayers are with all New Zealanders."
Heartbroken New Zealanders lit candles and placed flowers at makeshift memorials set up in the city.
Prime Minister Jacinda Ardern said the shooter had chosen to strike in New Zealand "because we represent diversity, kindness and compassion."