He was found not guilty of the more serious charge of second degree murder.
The jury of 10 men and two women, which was sequestered, began deliberations Monday and reached their verdict after about 11 hours.
It is the first time a police officer in Minnesota has been convicted over an on-duty shooting.
A USA police officer who shot dead an Australian woman in 2017 was found guilty of murder on Tuesday by a Minneapolis jury. Sentencing is scheduled for June 7.
The death of Damond, a life coach who was engaged to be married a month after the shooting, sparked outrage in both the USA and Australia.
In his only public statement about the shooting, Noor testified that after he heard the loud noise, he saw fear in Harrity's eyes and heard his partner yell, "Oh Jesus!" as he went for his weapon. He was found not guilty of intentional second-degree murder. "I fired one shot", he said before adding, "My intent was to stop the threat and save my partner's life".
Neither officer had a body camera running when Damond was shot, something Harrity blamed on what he called a vague policy that didn't require it.
Noor's defense attorneys argued throughout the monthlong trial that he fired to protect his terrified partner after hearing a thump on the squad vehicle in the alley and then seeing a figure by the driver's side window raising an arm.
Noor, who was in the passenger seat of the squad auto, shot Damond through the open window on the driver's side after he and Harrity were "spooked" by a noise, Hennepin County Attorney Mike Freeman said.
Noor was sacked after being charged in the case.
During Noor's trial, prosecutors had argued that the former officer violently gunned Damond down through the open driver's side window when she appeared on the side of the squad auto, claiming he abused his authority to use deadly force.
Noor, 33, had been charged with second-degree murder, third-degree murder and manslaughter.