Nintendo said that on the game's release day, it sold 874,000 copies.
Nintendo of America EVP of sales and marketing Cammie Dunaway called the game a "cultural phenomenon."
The title is currently earning an impressive 95/100 average review score on Metacritic.
The previous Smash Bros. title, Super Smash Bros. Melee for GameCube, was the best-selling GameCube title with 7 million units sold.
When Brawl launched in Japan on January 31, the title topped the million-mark in 11 days.