Train stations at Belmore, Lakemba and Punchbowl in southwest Sydney, Cardiff and Cockle Creek in Newcastle's western suburbs and Woy Woy on the Central Coast are now part of the plan to build new homes within 400 metres of the stations.
Premier Chris Minns said the reforms - the largest rezoning of land in Sydney's history - will deliver more than 170,000 homes across metropolitan Sydney.
"If we don't build more houses, young people will up and leave because they can't afford a home ... and if we lose our young people, we lose our future," he said on Friday.
The additions came after local councils suggested sites to be fast-tracked for development, he added.
The government announced new policies in December hoping to deliver thousands of new homes within 400m of 31 train stations in 13 local government areas.
All but one of those councils have engaged with the planning department to develop plans to deliver more housing, with some even requesting additional stations, the government said.
The six additional sites announced on Friday are in the Lake Macquarie, Canterbury-Bankstown and Central Coast local government areas.
Two more stations at Unanderra and Coniston in Wollongong could be included following further analysis of the water and wastewater capacity in the area.
The consultations have considered existing infrastructure and planned capacity upgrades to support increased density.
Committee for Sydney chief executive Eamon Waterford welcomed the news.
"When this program was announced, we said it was big, bold and blunt," he said.
"With the announcement that 12 councils have entered into agreements with the NSW government to deliver joint housing strategies, I'm willing to upgrade this to big, bold and balanced.
"The expansion of the ... program to an additional six locations is a welcome upgrade."
Planning Minister Paul Scully thanked the councils which worked collaboratively with the government on additional sites.
The opposition has previously criticised the government's planning policy as a "one-size-fits-all" approach.