The union representing the 750 workers says talks collapsed because the city refused to back down from demands for concessions including work hours, contracting out and retiree benefits.
The Canadian Union of Public Employees says the employees, who work in areas that include administration, building inspections, bylaw enforcement, tourism and road construction, will set up picket lines on Monday.
The city issued a statement saying it wants greater "operational flexibility" to better provide services to Londoners.
It says the city also offered wage increases to workers each year and improvements to employee benefits.
The city is promising to post details on its website on what services will be affected and says it remains willing to negotiate.
"It is obviously disappointing," Mayor Matt Brown said in a statement. "We wanted to continue working toward a fair and sustainable deal that would improve services for Londoners and we wanted to see our employees at work on Monday."
CUPE 101 Union President Shelley Navarroli said it was clear the city was not listening.
"Once again, this employer has shown that they have no intention to bargain, but to push our members on the picket line," she said in a release.
"Unfortunately, it is the community that our members serve that will suffer, because of management's tactics."