Morrison recently apologised for a Hawaiian holiday that ended early after public outrage.
He went on a tour of the New South Wales Rural Fire Service, whereby the volunteers have been struggling to contain blazes.
The PM faced flak for going on a family holiday amid the national crisis which has cloaked major cities like Brisbane and Sydney.
"I get it that people would have been upset to know that I was holidaying with my family while their families were under great stress... If you had your time over again and the benefit of hindsight we would have made different decisions," he said.
"I apologise," he said. "There have been lessons learned this week," adding that he believed it was time to move on from the controversy.
"I'm sure Australians are fair-minded and understand that when you make a promise to your kids, you try and keep it," the conservative leader said by way of explanation.
Watch: Catastrophic fires sweep across Australia
The embattled prime minister again acknowledged some link between climate change and weather patterns that scientists say has fuelled the fire crisis, but he indicated there would be no change in pro-coal policies.
Morrison also praised volunteer firefighters, who in the last 24 hours have faced catastrophic conditions brought by a record heatwave, gale-force winds and prolonged drought.
Australia's firefighting force is overwhelmingly made up of volunteers who have been strained by the intensity and the length of this year's fire season.
Officials said two fires, already big enough to create their own thunderstorms, to the southwest of Sydney had joined to form another "megafire" on the doorstep of Australia's largest city.
Conditions eased markedly on Sunday, giving them time to try to contain massive blazes near Sydney that are only likely to be extinguished with heavy rainfall.
The news of his vacation has recently triggered protests. People on social media used the hashtag #WhereTheBloodyHellAreYa?