Jami Resch, who was barely six months into her job as chief, said she has asked Charlie Lovell, an African-American lieutenant, to serve as the next chief of police of Oregon's largest city.
"He's the exact right person at the exact right moment.," she said at a news conference.
Resch said she would remain at the bureau but her role had yet to be determined, Fox 12 reported.
A protest that lasted until the early hours of Monday eventually turned unruly, resulted in at least 20 arrests. Some people allegedly threw objects at police, who fired tear gas and sponge-tipped projectiles.
Full beverage containers, glass bottles, hard-boiled eggs, and rocks were thrown or fired at officers using slingshots, police said in a statement Monday. A medic who was working with the officers was hit in the stomach with a rock.
The incident unfolded by the Justice Center in downtown Portland.
The ACLU of Oregon has called on Portland police to end the use of tear gas, impact weapons and flash-bang devices.
"We join the protesters in calling for a new approach in our community, and demanding that we uphold the rights of people who have historically had their rights and humanity denied," the rights group said Sunday.
City Commissioner Jo Ann Hardesty slammed the recent police response.
"I'm incredibly troubled by the excessive force used nightly by PDX police since the protests began," she said. "The videos and painful firsthand accounts of community members getting tear-gassed and beaten by police for exercising their 1st amendment rights should be concerning for us all."
The Associated Press contributed to this report.