Cartoon police characters A Ling and Jin Jin started "duty" on Tuesday, keeping "watch" over crowded public venues and warning people against theft.
The first five pairs of police cardboard cutouts have been placed in both large stores and restaurants along Xizang Road and Fuzhou Road in Huangpu District.
More of their "colleagues" will be placed in other commercial areas in the district.
Police said cartoon police boast advantages over former anti-theft methods such as leaflets or broadcasting monotonous messages.
"They can remind people to take good care of their personal belongings," said Zhu Weigang, director of Jinling Road E. Police Station.
Their cute appearance even helps citizens feel the warmth of the city's finest, Zhu said.
Residents said they are pleased to see the newcomers.
"It is a great idea to have such cute police around when you go shopping," said Zhang Zhizhu. "When I see them I will watch my purse more carefully."