At least 17 people died while three others were seriously injured after the bus they were travelling in overturned, 600 kilometres north of Ethiopian capital, Addis Ababa, police said Wednesday.
The passengers were on their way to a religious festival when the accident occurred.
Police said the bus, with 20 people on board, fell into a ditch, trapping the passengers inside.
The three survivors were rushed to a nearby hospital in the northern district of Amara Sayent.
Ten of the deceased have since been buried in a monastery, venue of the ceremony they were attending.
The remaining bodies were given to families and relatives.
Ethiopia has one of the highest accidents rates in the world, with more than 2,000 people dying annually, while tens of millions worth of property is damaged.
Lack of traffic signs, poor performance of drivers and roads as well as the high number of old cars, experts say, contribute to the high number of traffic accidents in the country, home to around 80 million people.
In Addis Ababa an average of two people die daily from traffic accidents, making it one of the deadliest cities in the world to drive in.