The stakes could not be much higher for the 69-year-old right-wing leader who, as in April polls, faces a strong challenge from ex-military chief Benny Gantz and his centrist Blue and White alliance.
Netanyahu voted in Jerusalem and said he expected a close election, urging Israelis to turn out in large numbers.
US "President (Donald) Trump said yesterday that the elections will be tight," Netanyahu said, referring to comments by his staunch ally who called the polls "50/50".
"I can guarantee you this morning that they are very tight."
He spent the day warning he was on the verge of losing if his supporters did not turn out to vote, including in appearances at Jerusalem's main market and its central bus station, where he wielded a megaphone to exhort the crowds.
He repeatedly warned, as he has in previous elections, that left-wing and Arab voters were showing up in large numbers to vote him out.
Gantz voted in his hometown of Rosh Haayin near Tel Aviv and called on the country to reject corruption and "extremism".
"We want new hope. We are voting today for change," Gantz said after voting with his wife Revital.
"We will succeed in bringing hope. We will succeed in bringing change, without corruption and without extremism, all together."
Later he visited a shopping mall in the northern city of Haifa and wielded a bullhorn along the beach in Tel Aviv.
Polls were due to close in most areas at 10:00 pm (1900 GMT), with some 6.4 million people eligible to vote.
The first exit surveys will be released just after polls close, while official results are not expected until Wednesday.
There were signs that concerns over election fatigue had not materialised.