The actress, who plays Myrtle Wilson in the new film by Baz Luhrman, chose an elegant Prada dress for the Catherine Martin and Miuccia Prada Dress Gatsby Opening Cocktail event.
The dress featured a round neckline, three-quarter length sleeves and a modest hemline. She paired the frock with an embellished clutch bag and black patent platform heels.
To finish off the look, Fisher wore her auburn locks in loose waves.
Also in attendance at the star-studded event was her co-star Carey Mulligan, who chose a demure black Prada dress.
She was joined by Florence Welch of Florence and the Machine, who chose a chic black suit with a striped shirt and white brimmed fedora.
Fashion icon Alexa Chung was similarly chic in a black, A-line dress which featured gold embellishments at the neck and pockets.
Tobey Maguire, who plays the novel's narrator Nick Carraway in the film, was accompanied by his wife Jennifer Meyer, who chose an artfully creased dress for the event.
Popstar Katy Perry went for a ladylike print dress and bow sandals.
Maggie Gyllenhaal looked fabulous in a white cocktail dress which featured ruffles at the bust and arms.
Jennifer Meyer, Isla Fisher and Amanda de Cadenet posed together for photographers.