Prime Minister Benjamin Netanyahu called the snap election after failing to form a governing coalition with a viable majority after April's vote.
The final opinion polls put his right-wing Likud party neck and neck with its main challenger, the centrist Blue and White party led by former military chief Benny Gantz.
Smaller parties could therefore have a big say in the final outcome.
Negotiations on the formation of a new coalition are expected to start as soon as voting ends at 22:00 (19:00 GMT) and exit polls are published.
Likud and Blue and White came away with 35 seats each in the 120-seat Knesset.
Mr Netanyahu declared victory and it appeared that he would be able to secure a majority with the backing of smaller right-ring and religious parties. But after several chaotic weeks the attempted coalition-building collapsed into recriminations.