The vote follows the police chief's decision to fire an officer, who shot and killed a mentally ill man in a downtown park, in April.
The officers voted late Thursday, at Serb Hall. Their union President Mike Crivello announced the results Friday morning at city hall. He says about 99 percent of the union members voted against Chief Edward Flynn.
He fired officer Christopher Manny for failing to follow procedures when confronting a mentally ill person.
Dontre Hamilton had been sleeping in Red Arrow Park downtown, when a nearby worker summoned police. The first two officers to arrive left, after determining the 31-year-old was not a threat.
When Manney later responded to the call, he started patting down Hamilton, who began to struggle with the officer and reportedly took his baton and hit him. Manney then shot Hamilton 14 times, killing him.
As for the impact of the police union's no-confidence vote in the chief, it is largely symbolic, according to Stan Stojkovic, dean of UWM's Helen Bader School of Social Welfare.
"They want to be heard," he says, of the rank-and-file officers.
"Some of this is really around how police officers do their job. There has always been disagreement about things, but the disagreement plays itself out, when a tragedy occurs," Stojkovic says.
Stojkovic says the chief will have to try to address officer morale, over the long term. "They may be upset with the police chief, but the police chief is required by law to make these tough decisions," Stojkovic says.