The new date still falls in the middle of the rainy season, reinforcing logistical concerns about elections seen as critical to the political transition under Prime Minister Abiy Ahmed.
"As per the allowed legal provisions, we've decided to revise the electoral date to August 29," electoral board chair Birtukan Mideksa said Friday.
"We will work with the National Meteorology Agency of Ethiopia to mitigate the impact of the rainy season on the electoral schedule," she said, according to state-affiliated Fana Broadcasting Corporate.
It was not clear how officials planned to overcome the inevitable challenges posed by holding elections at a time when many of the country's roads are impassable.
Abiy, who won the Nobel Peace Prize last year, believes the election will give him a mandate for wide-ranging political and economic reforms.
He was appointed prime minister in 2018 after several years of anti-government protests.
He rose through the ranks of the Ethiopian People's Revolutionary Democratic Front (EPRDF) ruling coalition, which dominated parliament and allowed only one competitive election after it took power in the early 1990s, which was in 2005.
The EPRDF and its allies won all 547 seats in parliament in 2015.
However the coalition no longer exists following Abiy's decision to transform it into a single political group, the Ethiopian Prosperity Party.
According to the new schedule, campaigning is set to begin on May 28, and final results will be made available no later than September 8.
Some opposition parties and civil society representatives say they are worried about the readiness of the electoral board and the security situation in Ethiopia, which has struggled to curb ethnic violence.