The 38-year-old Israeli-born actress hit the red carpet on Sunday in a cape that had the names of snubbed female directors embroidered into it, as a form of activism.
McGowan, who is known for speaking her mind, fired shots at Portman and her gesture on Tuesday evening.
"Some thoughts on Natalie Portman and her Oscar 'protest.' The kind of protest that gets rave reviews from the mainstream media for its bravery. Brave? No, not by a long shot. More like an actress acting the part of someone who cares. As so many of them do," she said at the beginning of her post.
The former Charmed regular continued her lengthy commentary by stating that she was "singling" Portman out because she is "the latest in a long line of actresses who are acting the part of a woman who cares about other women."
"Actresses who supposedly stand for women, but in reality do not do much at all," she continued.
Portman responded earlier today via a statement she sent to The Wrap.
She began by stating that she agrees with McGowan in that she does not consider her decision to wear the garment as "brave" and asserted that she instead reserves the term for women such as those who are testifying against Harvey Weinstein.
McGowan, 46, was one of the first people to come forward and speak out against Weinstein in October 2017, setting off a domino effect that led to many other actresses speaking out against the Hollywood mogul. He is currently facing several criminal charges for sexual assault and other felonies in the state of New York, per The Inquisitr.
Portman also addressed other statements McGowan made in her post, such as how she hardly ever works with female directors and that her production company has only ever hired one female director, that director being the actress herself.
Portman said that it is true that she has only worked with a few women -- naming the likes of Marya Cohen, Mira Nair, Rebecca Zlotowski, Anna Rose Holmer, Sofia Coppola, and Shirin Neshat -- because "unfortunately," the films she has tried to make are a "ghost history."
The New York I Love You star asserted that even if women do get the financing or opportunity to make movies, they then face other obstacles such as getting into festivals or getting recognition at award ceremonies. Portman then proclaimed that she has tried and will keep on trying.
Some of the names who were scripted in Portman's black cape include Lorena Scafaria (Hustlers), Lulu Wang (The Farewell), Greta Gerwig (Little Women), Marielle Heller (A Beautiful Day in the Neighborhood), Alma Har'el (Honey Boy) and Céline Sciamma (Portrait of a Lady on Fire).