The brunette beauty attended a promotional party for her new fragrance, True Reflection, at the London Hotel in West Hollywood and was posing for pictures when a woman threw white powder at her.
The flour covered her hair and back, and Kardashian was escorted to a private room to clean up.
The Los Angeles Fire Department was called to examine the powder, but they quickly determined it was just ordinary cooking flour, according to TMZ.com.
The woman was detained by police officers over the incident, although as WENN went to press, it was not known if she was charged with an offence.
Kardashian returned to the event after changing.
After hearing of the incident on Twitter.com, Kardashian's sister Kourtney wrote, ""Classy to flour bomb my sister at her charity event helping women. I wonder if they would have dared thrown the flour at my hormonal and pregnant self!""