City council voted 5-0 to demolish the old Siouxland YMCA building.
The city's code enforcement red-tagged the building last winter because of safety issues and break-ins.
Building owner, Paul Bernard, previously proposed to turn the structure into office space that would provide 300 jobs to the area.
Bernard said renovations would cost $3.3 million, but city officials say he is still looking for funding sources.
"It is nice that they went ahead and got the order for demolition on it, because it is, simply because it is an unsafe structure," said Sioux City Code Enforcement Manager Darrel Bullock. "It is dangerous. Open stairways, open elevator shafts, as well as other hazards, such as asbestos that's airborne in there once there's foot traffic in the building."
City officials say the building could cost up towards $200,000 to demolish.
They say it's likely the building is still a year out from demolition.