Early results showed the party had picked up a newly created inner-city seat, retaining another and was expected to secure a further two seats on the north coast.

Greens upper house MP John Kaye said on Saturday night the party was extremely pleased with the results.

"The results exceed my wildest expectations," Dr Kaye said.

"It is a seachange for the Greens. We now have three, possibly four seats in the lower house and the people who wrote off the Greens as a political force will have to go back and rewrite their obituaries."

Dr Kaye said he was also very pleased that the "people of the north coast and inner city will have a voice that is uniquely theirs".

Greens supporters were triumphant at their election event at the grandstand at the Sydney University Oval, at one stage chanting "Four, Four, Four, Four!" to mark their hopes of winning Newtown, Balmain, Lismore and Ballina.

Newtown is a new seat and the smallest in the state. It was created because of the rapid inner-city population growth and takes in suburbs from Surry Hills and Redfern to Stanmore and Petersham.

Greens candidate Jenny Leong won the seat with a two-party preferred vote of 60 per cent to Labor's 39 per cent.

Ms Leong was jubilant at her win, telling her supporters at a gathering at Sydney University that  "we have the chance in Newtown to reshape the progressive agenda in NSW".

She also committed to retaining Aboriginal Housing at the Block in Redfern.

The former Amnesty International campaigner listed a number of other areas she would fight for. "This win in Newtown means there will be no WestConnex," she said, in reference to the motorway proposal the Greens have campaigned to scrap.

Incumbent Greens candidate Jamie Parker has secured the seat of Balmain after a tight two-way contest with the Labor Party's Verity Firth.

Early results put Parker ahead of Firth by 6 per cent, Fairfax Media's vote tracker showed, with Verity Firth conceding defeat by 9.30pm.

Mr Parker, the first Greens member to win a lower house seat in the NSW Parliament, is a popular former mayor of Leichhardt Council and reflects the progressive views of the majority of voters on the Balmain peninsula. He said his party had been successful in opposing the government's moves to evict the Glebe Youth Service and downgrade services at Balmain Hospital.

Mr Parker said the Greens' fight against the corruption that has plagued the major parties had contributed to its success at the polls.

"We have been corruption fighters," he said on Saturday night. "Labor and Liberal have disgraced themselves. And we have been standing up there in the Parliament saying that MPs need to be held to account.

"And the first piece of legislation that I'll be moving is to criminalise bribery and misconduct for public officials to make sure that people like Eddie Obeid ... actually get to face the music in a real way."

The seats of Lismore and Ballina were also the subject of tight battles. The Greens' Adam Guise  looked set to take the seat from the Nationals' Thomas George with a 26 per cent swing. George had held the seat since 1999 but there had been a backlash against Mr George and his pro coal-seam-gas mining stance.

In Ballina the Greens candidate Tamara Smith was predicted to take the seat, which had been held by the Nationals' Don Page, who had been in Parliament for 27 years. There was a 31 per cent swing against them.

with Jacob Saulwick