Far behind in second place, the Open Road Films' "Home Again" opened with an estimated 9.02 million US dollars.
Final weekend numbers show the supernatural horror film clearing $123.1 million in its North American debut for New Line and Warner Bros.
With the record-breaking opening for "It" and potentially strong titles on the docket for the rest of the year, there's renewed hope that the box office can get back on the right track before year's end.
"A terrific start for the Fall moviegoing season after a rather slow Labor Day weekend as 'It'revs up a sleepy marketplace and we look forward to an fantastic September at the box office, " wrote movie analyst Paul Dergarabedian at comScore in an email to Xinhua.
The film now has the largest September opening in cinematic history, the largest fall opening ever, and the largest opening weened for an R-rated horror movie. Finally, IT is second for all R-rated movie launches, behingd Deadpool, which opened in 2016 with $132.4 million.
"It" was directed by Andy Muschietti, who is already being courted for another instalment.
Time Warner Inc's Warner Bros. had relatively modest expectations when it started making "It", which is why it spent only $35 million on production.
Audience scores are as high as they get for the horror genre so positive word-of-mouth will lead to plenty of more business ahead. Coming in at third was Hitman's Bodyguard, which fell to third place this weekend.
IT also received positive reviews, including 87% on Rotten Tomatoes and a B+ CinemaScore. It's also the biggest opening weekend from a horror film beating out previous record-holder 2011's Paranormal Activity 3 with its $52.6 million. This weekend, Homecoming dropped 45.3 percent to bring in another $2 million.
The film's success is good news not just for Warner, but all of Hollywood. The worldwide sum hit $495.3M while the global gross rose to $823M passing the $816.3M of Wonder Woman in the process.
Money-wise, it's hard to see how any of the three big releases next weekend will come close either.
The movie adapts only part of the 1,000-plus page book, in which its main characters are children.