Gladys Berejiklian will become the first female premier to be re-elected in NSW, a 9News exclusive exit poll shows.

However, there is a strong chance the Coalition will be forced into a minority government .

The YouGov Galaxy exit poll shows a two-party preferred result of 50-50 between Labor and the Coalition - a swing to Labor of around three per cent compared to 2015.

Michael Daley casts a ballot on election day. (9news)

As a consequence, a hung parliament and a minority government is a likely outcome.

A deadlock will favour the government, with several of the existing independents likely to back the Coalition.

The poll indicates we may not know the winner tonight.

Voters will continue to cast their ballots until 6pm, with the count likely to begin 30 minutes later.

Gladys Berejiklian is likely to be the re-elected as premier. (9news)

Primary support for the Coalition is 41 per cent, according to the poll, a five point decline from the 2015 win.

But Labor is behind them, reporting 36 per cent of the primary vote.

The Greens are polling at nine per cent, with most of their preferences flowing to Labor.

The swing from the Coalition would put six of their seats at risk, which would cost them their majority in parliament.

Only a mild swing would not be in line with the double-digit swings that the Coalition have faced against them in by-elections in the last few years, Nine political editor Chris Uhlmann said.

“Once upon a time that was unheard of,” he said.

“If this is the case then they have stemmed the tide of bleeding from the past few years.”

The exit poll indicates the Coalition will not pick up any of Labor’s most marginal seats, however.

Health and hospitals is the biggest issue for voters, with 43 per cent citing it as a major concern.

Education comes in second at 35 per cent, followed by traffic and public transport, both on 23 per cent.