The figure beats the previous best of 1,127,033, which stood for 31 years, and was set in 40 fewer games.
“The NBL is the fastest growing sporting league in Australia and smashing our attendance record is further validation of the world-class entertainment product our competition has become,” said NBL chief executive David Stevenson.
“The fans are the lifeblood of the competition and are at the forefront of every decision we make. There would be no NBL without the fans, so I want to thank each and every one of them who attended a game this season and helped us create history. Your passion, dedication and commitment is unmatched.
There have been 54 sell-outs in the NBL this season, with a capacity crowd of 10,300 at the John Cain Arena clinching the new record.
Fans witnessed the Illawarra Hawks defeat Melbourne United 80-71 in Game 4 of the Championship Series to take it to a title decider on Sunday (March 23).
“I want to thank and highlight our clubs, who do an amazing job at elevating the game-day experience and connecting to their supporters in the best way possible,” Stevenson continued.
“While we continue to set records, our ambitions remain high, and with some exciting announcements to come, we look forward to even bigger and better things in the future.”
The NBL played its first season in 1979 as the National Invitation Basketball League before adopting the current name the following year.
In October, the New Orleans Pelicans, from the North American National Basketball Association (NBA), is set to play NBL sides Melbourne United and South East Melbourne Phoenix as part of an exhibition series.