About 700 transit bus drivers for Quebec City have been on strike since Saturday, stranding commuters and crippling transit service in the city.
Union representatives said drivers rejected the municipal bus authority's latest contract offer Monday night by a vote of 81%.
Salaries lie at the heart of the dispute, with drivers demanding wages more in line with those of drivers in Montreal. The city says it cannot afford the increase.
Drivers walked off the job after an appointed conciliator failed to secure an agreement between parties.
No new talks are scheduled between the two sides.