Neighbors took in $51.1 million in domestic ticket sales, making it the fourth-largest opening for an R-rated comedy.
The film, which stars Rogen and Rose Byrne as a married couple at odds with the leader of a fraternity house next door, blew past box-office estimates of $35 million.
The Amazing Spider-Man 2, which debuted only last weekend, took second place with $37.2 million.
"What people weren't expecting was it to be blown out of first place by Neighbors," analyst Tim Briody, of Box Office Prophets, told USA Today.
Despite positive buzz for Neighbors, analysts still thought Spider-Man would hold on to No. 1 until Godzilla opened on May 16.
The Other Woman rounded out the top-three with $9.3 million.