Wilson struck a series of comical martial arts poses as he entertained passers-by.
Crowds swarmed the windows in an attempt to photograph the pair after Stiller informed fans of the stunt on Twitter.
He posted: “Hey #Rome I hear Derek #Zoolander and Hansel are modeling at #Valentino store window in a little while.”
The pair have taken part in several stunts to promote the hotly anticipated sequel.
Blue Steel: Ben Stiller strikes a pose in the window of Valentino Getty
Ernesto Ruscio/Getty
They announced news of a second film by walking the Valentino catwalk at Paris Fashion Week in March last year, and Stiller worked his best Blue Steel for a FIAT commercial.
The film will see Will Ferrell reprise his role as Mugatu while stars including Penelope Cruz, Kristen Wiig, Billy Zane and Justin Bieber also make an appearance.
Zoolander 2 is set for UK cinema release on February 12.
