And the similarities don't end there: they are notable actresses and have daughters around the same age. Adams is mom to 3-year-old Aviana with fiancé Darren Le Gallo, while Fisher has 6-year-old Olive and 3-year-old Elula with hubby Sacha Baron Cohen.
But the look-alike comparisons don't really make much sense to Adams, who reveals to Vanity Fair that she doesn't understand why people confuse them.
"I get Isla Fisher all the time, still," the American Hustle star tells the January issue of the magazine about her doppelganger. "And I know Isla, and for a while our kids went to the same dance school."
"When I'm with Isla, we both look at one another and say, ‘I get it but I don't get it,'" the 39-year-old Academy Award nominee adds.
After all, Adams has pale blue eyes and Fisher has brown eyes. And if you listen to them speak, they sound nothing alike: Adams is American, while Fisher hails from Australia.
But differences aside, Adams jokes that there could be less attractive people to be compared to, without naming names, of course.
"But just like I tell her, it could be a lot worse," Adams says. "I could be mistaken for a lot worse people."
Adams looks positively radiant and ready for the holidays on the cover, donning a low-cut red frock and dark lips, while holding up a glittering gold Christmas tree ornament.
The new issue of Vanity Fair is on sale now.