Workers could be seen building a Christmas market in the Trongate area of the city on Tuesday, while others hung Christmas decorations in a shop window and painted out street names.
Art director Nigel Evans and production designer Christopher Glass were seen walking around the area on Tuesday.
Road closures will be in place in the Merchant City area of Glasgow over several days in January for filming.
Batgirl will focus on Barbara Gordon, the daughter of Gotham police commissioner Jim.
The movie, expected to debut on the HBO Max streaming service in 2022, will be directed by Bad Boys For Life filmmakers Adil El Arbi and Bilall Fallah.