The Ethiopia election board has extended voting to 21:00 local time (18:00 GMT) in areas where people are still queuing.
The board said 37m voters had registered and high turnout has been reported in several cities.
Ideally 547 MP seats would be contested but the authorities cancelled races in 102 constituencies because of insecurity and logistical challenges in some regions, including the war-torn northern region of Tigray.
Some 42,000 polling stations opened on Monday, with one polling station serving a maximum of 1,500 people.
Counting starts as soon as voting ends and results will then be posted on a notice board and sent to centres in each constituency. They will then be collected, collated and announced by the electoral board within 10 days.
Prime Minister Abiy Ahmed's Prosperity Party is the favourite to win a majority of seats in parliament.
His closest challenger is Berhanu Nega, the leader of Ethiopian Social Justice Party, which has fielded 1,385 candidates in the regional council and federal parliament seats.
The African Union and other foreign observers have been monitoring the polls but not the European Union.