Notably missing is actress Kim Catrall, who played Samantha Jones, as she will not take part in the revival.
Parker, 56, shared on her Instagram a photo of the three main characters, revealing they had been reading through the first episodes, "alongside all the fellas and our newest cast members".
"Friendship never goes out of style," Nixon, 55, wrote, sharing the same photo on her social media.
Parker also said that she arrived at the table read "way too early", her "nerves all a wonderful jumble".
Also present were fan favourites Chris Noth (John James "Mr Big" Preston), Willie Garson (Stanford Blatch), and Mario Cantone (Anthony Marentino).
"Everyone at And Just Like That … is thrilled to be able to continue the storylines of these beloved Sex and the City characters with the actors who made them so lovable," Executive Producer Michael Patrick King said in a statement earlier this week, announcing the return of these three characters.
On social media, people pointed out Catrall's absence from the revival, with many worrying the show will not be as good without her.
The iconic series ended in 2004, and has since had two successful movie sequels.
